Our **system** is simply our chemical reaction. Anything outside of that is considered our **surroundings**.

Concept #1: Thermodynamics vs. Thermochemistry

**Thermodynamics** deals with the conversion of energy from one form to another. **Thermochemistry** is the branch of chemistry dealing with thermal (heat) energy.

Concept #2: System vs. Surroundings

Example #1: Whether our system (the chemical reaction) **releases** or **absorbs** heat or energy will determine if it is **exothermic** or **endothermic**.

Example #2: Classify each of the following process as either **exothermic **or **endothermic:**

a) Fusion of Ice.

b) Sublimation of CO_{2}.

c) Vaporization of aqueous water.

d) Deposition of chlorine gas.

e) Condensation of water vapor.

Concept #3: Understanding the internal energy of the system

The **internal energy (ΔE or ΔU)** of the system can be calculated from the **heat **and **work** of the system.

Concept #4: Heat vs. Work

The signs of **heat (q)** and **work (w)** of the system can be either negative or positive depending on the key words stated.

Example #3: Which of the following signs on q and w represent a system that is doing work on the surroundings, as well as losing heat to the surroundings?

q = - , w = - q = +, w = +

q = -, w = + q = +, w = -

**Work **is one key variable to find the **internal energy** of the system. It’s equals to **– PΔV**.

Concept #5: Calculating work

Once we’ve calculated **work** we can calculate the **internal energy** of the system once we also calculate the **heat **released or absorbed.

Concept #6: Calculating heat and the internal energy of the system

Under certain conditions either **q (heat)** or **w (work)** can be equal to zero. This makes it easier to calculate the **internal energy** of the system.

Concept #7: Calculating the internal energy of the system in a vacuum

When **work **is done against a **vacuum** the pressure is equal to **0 atm**. Since **ΔE = q + w**, the equation becomes only **ΔE = q**.

Practice: The reaction of nitrogen with hydrogen to make ammonia has an enthalpy, ?H = - 92.2 kJ: N2 (g) + 3 H2 (g) ----> 2 NH3 (g) What is in the internal energy of the system if the reaction is done at a constant pressure of 20.0 atm and the volume compresses from 10 L to 5 L?

Which statement is not correct?
a. Internal energy, E, is a state function.
b. Heat and work are state functions.
c. Heat is given off to the surroundings in an exothermic reaction.
d. The enthalpy change is the heat of reaction at constant pressure.
e. Enthalpy is a state function.

1 L.atm =101.325 J
When 2.00 kJ of energy is transferred as heat to nitrogen in a cylinder fitted with a piston at an external pressure of 2.00 atm, the nitrogen gas expands from 2.00 to 5.00 L against this constant pressure. What is ∆U for the process?
1. 0
2. −0.608 kJ
3. +1.39 kJ
4. +2.61 kJ
5. −2.61 kJ

DO NOT FORGET TO WRITE A BALANCED CHEMICAL EQUATION!!
The combustion of one mole of octane (C8H18(l)) to produce carbon dioxide and liquid water has ∆Hr = −5471 kJ · mol−1 at 298K. What is the change in internal energy for this reaction?
1. −5460 kJ · mol−1
2. −5493 kJ · mol−1
3. −5471 kJ · mol−1
4. −5449 kJ · mol−1
5. −5482 kJ · mol−1

A system releases 415 kJ of heat and does 125 kJ of work on the surroundings. What is the change in internal energy of the system?

The gas in a piston is warmed and absorbs 655 J of heat. The expansion of the piston performs 344 J of work on the surroundings. Find the change in internal energy of the system.

The change in enthalpy (∆H) is a measure of the heat of reaction at
1) Constant temperature.
2) Constant pressure.
3) Constant volume.
4) Constant internal energy.
5) Constant entropy.

What is internal energy?

Is internal energy a state function?

In which direction does energy flow?

What is heat?

Explain the difference between heat and temperature.

How is the change in internal energy of a system related to heat and work?

Explain how the sum of heat and work can be a state function, even though heat and work are themselves not state functions.

What is pressure-volume work?

Identify each of the following energy exchanges as primarily heat or work and determine whether the sign of E is positive or negative for the system. a. Sweat evaporates from skin, cooling the skin. (The evaporating sweat is the system.) b. A balloon expands against an external pressure. (The contents of the balloon is the system.) c. An aqueous chemical reaction mixture is warmed with an external flame. (The reaction mixture is the system.)Identify energy exchanges as primarily heat or work.

A gas-phase reaction was run in an apparatus designed to maintain a constant pressure.
Predict whether w is positive, negative, or zero.

Identify each of the following energy exchanges as primarily heat or work and determine whether the sign of E is positive or negative for the system. a. Sweat evaporates from skin, cooling the skin. (The evaporating sweat is the system.) b. A balloon expands against an external pressure. (The contents of the balloon is the system.) c. An aqueous chemical reaction mixture is warmed with an external flame. (The reaction mixture is the system.)Determine whether the sign of E is positive or negative for the system.

A gas is confined to a cylinder fitted with a piston and an electrical heater, as shown here:
Suppose that current is supplied to the heater so that 100 J of energy is added. Consider two different situations. In case (1) the piston is allowed to move as the energy is added. In case (2) the piston is fixed so that it cannot move.
You may want to reference (Pages 167 - 172) Section 5.2 while completing this problem.In which case does the gas have the higher temperature after addition of the electrical energy?

A gas is confined to a cylinder fitted with a piston and an electrical heater, as shown here:
Suppose that current is supplied to the heater so that 100 J of energy is added. Consider two different situations. In case (1) the piston is allowed to move as the energy is added. In case (2) the piston is fixed so that it cannot move.
You may want to reference (Pages 167 - 172) Section 5.2 while completing this problem.Identify the sign (positive, negative, or zero) of q and w in case (1).

A gas is confined to a cylinder fitted with a piston and an electrical heater, as shown here:
Suppose that current is supplied to the heater so that 100 J of energy is added. Consider two different situations. In case (1) the piston is allowed to move as the energy is added. In case (2) the piston is fixed so that it cannot move.
You may want to reference (Pages 167 - 172) Section 5.2 while completing this problem.In which case is E for the system (the gas in the cylinder) larger?

A gas is confined to a cylinder fitted with a piston and an electrical heater, as shown here:
Suppose that current is supplied to the heater so that 100 J of energy is added. Consider two different situations. In case (1) the piston is allowed to move as the energy is added. In case (2) the piston is fixed so that it cannot move.
You may want to reference (Pages 167 - 172) Section 5.2 while completing this problem.Identify the sign (positive, negative, or zero) of q and w in case (2).

Explain the significance of the law of conservation of energy.

Which of the following cannot leave or enter a closed system: heat, work, or matter?

What do we call the part of the universe that is not part of the system?

Which cannot leave or enter
an isolated system?

The accompanying photo shows a pipevine swallowtail caterpillar climbing up a twig.
As the caterpillar climbs, its potential energy is increasing. What source of energy has been used to effect this change in potential energy?

The accompanying photo shows a pipevine swallowtail caterpillar climbing up a twig.
If the caterpillar is the system, can you predict the sign of q as the caterpillar climbs?

The accompanying photo shows a pipevine swallowtail caterpillar climbing up a twig.
Does the caterpillar do work in climbing the twig? Explain.

The accompanying photo shows a pipevine swallowtail caterpillar climbing up a twig.
Does the amount of work done in climbing a 12-inch section of the twig depend on the speed of the caterpillars climb?

Imagine a container placed in a tub of water, as depicted in the accompanying diagram.
If neither the volume nor the pressure of the system
changes during the process, how is the change in internal energy related to the change in enthalpy?

The accompanying photo shows a pipevine swallowtail caterpillar climbing up a twig.
Does the change in potential energy depend on the caterpillars speed of climb?

You lose 9 pounds over a 26-day period. Which of the following quantities act like a
state function: the amount of calories you consume, your weight, or the number of
calories burned through exercise?

According to the first law of thermodynamics, what
quantity is conserved?

What is meant by the internal energy of a system?

By what means can the internal energy of a closed system increase?

Consider a system consisting of the following apparatus, in which gas is confined in one flask and there is a vacuum in the other flask. The flasks are separated by a valve. Assume that the flasks are perfectly insulated and will not allow the flow of heat into or out of the flasks to the surroundings. When the valve is opened, gas flows from the filled flask to the evacuated one.Is work performed during the expansion of the gas?

Imagine that you are climbing a mountain.Is the distance you travel to the top a state function?

Imagine that you are climbing a mountain.Is the change in elevation between your base camp and the peak a state function?

Consider a system consisting of the following apparatus, in which gas is confined in one flask and there is a vacuum in the other flask. The flasks are separated by a valve. Assume that the flasks are perfectly insulated and will not allow the flow of heat into or out of the flasks to the surroundings. When the valve is opened, gas flows from the filled flask to the evacuated one.Can you determine the value of E for the process?

Consider the two diagrams below.
The equations you obtained in parts (a) and (b) are based on what law?

Consider the two diagrams below.
Would
similar relationships hold for the work involved in each
process? Why?

In the cylinder diagrammed below , a chemical process occurs at constant temperature and pressure.
You may want to reference (Pages 173 - 176) Section 5.3 while completing this problem. Is the sign of w indicated by this change positive or negative?

In the cylinder diagrammed below , a chemical process occurs at constant temperature and pressure.
You may want to reference (Pages 173 - 176) Section 5.3 while completing this problem.Given that the process is endothermic, does the internal energy of the system within the cylinder increase or decrease during the change, and is E positive or negative?

At 20 oC (approximately room temperature) the average velocity of N2 molecules in air is 1050 mph.What is the kinetic energy (in J) of an N2 molecule moving at this speed?

At 20 oC (approximately room temperature) the average velocity of N2 molecules in air is 1050 mph.What is the total kinetic energy of 1 mol of N2 molecules moving at this speed?

The air bags that provide protection in autos in the event of an accident expand because of a rapid chemical reaction. The air bags give off heat when they expand.From the viewpoint of the chemical reactants as the system, what do you expect for the signs of q and w in this process?

An aluminum can of a soft drink is placed in a freezer. Later, you find that the can is split open and its contents frozen. Work was done on the can in splitting it open.
You may want to reference (Pages 165 - 166) Section 5.1 while completing this problem.Where did the energy for this work come from?

A sample of gas is contained in a cylinder-and-piston arrangement. It undergoes the change in state shown in the drawing. Assume first that the cylinder and piston are perfect thermal insulators that do not allow heat to be transferred.
What can be said about E for the state change?

A sample of gas is contained in a cylinder-and-piston arrangement. It undergoes the change in state shown in the drawing. Assume first that the cylinder and piston are perfect thermal insulators that do not allow heat to be transferred.
Now assume that the cylinder and piston are made up of a thermal conductor such as a metal. During the state change, the cylinder gets warmer to the touch. What is the sign of q for the state change in this case? Describe the difference in the state of the system at the end of the process in the two cases. What can you say about the relative values of E?

A sample of gas is contained in a cylinder-and-piston arrangement. It undergoes the change in state shown in the drawing. Assume first that the cylinder and piston are perfect thermal insulators that do not allow heat to be transferred.
What is the sign of w for the state change?

Consider the systems shown in the following figure. In one case the battery becomes completely discharged by running the current through a heater, and in the other by running a fan. Both processes occur at constant pressure. In both cases the change in state of the system is the same: The battery goes from being fully charged to being fully discharged. Yet in one case the heat evolved is large, and in the other it is small.
Is the enthalpy change the same in the two cases?

In a thermodynamic study a scientist focuses on the properties of a solution in an apparatus as illustrated. A solution is continuously flowing into the apparatus at the top and out at the bottom, such that the amount of solution in the apparatus is constant with time.
Is the solution in the apparatus a closed system, open system, or isolated system?

In a thermodynamic study a scientist focuses on the properties of a solution in an apparatus as illustrated. A solution is continuously flowing into the apparatus at the top and out at the bottom, such that the amount of solution in the apparatus is constant with time.
If it is not a closed system, what could be done to make it a closed system?

A 200-lb man decides to add to his exercise routine by walking up three flights of stairs (45 ft) 20 times per day. He figures that the work required to increase his potential energy in this way will permit him to eat an extra order of French fries, at 245 Cal, without adding to his weight.Is he correct in this assumption?

Identify the force present, and explain whether work is being performed in the following cases.You lift a pencil off the top of a desk.

Identify the force present, and explain whether work is being performed in the following cases.A spring is compressed to half its normal length.

Identify the force present, and explain whether work is done in the following cases.A positively charged particle moves in a circle at a fixed distance from a negatively charged particle.

Identify the force present, and explain whether work is done in the following cases.An iron nail is pulled off a magnet.

Is a human being an isolated, closed, or open system?

Electrostatic potential energy. At finite separation distances for two charged particles, Eel
is positive for like charges and negative for opposite charges. As the particles move farther apart, their electrostatic potential energy approaches zero.A positively charged particle and a negatively charged particle are initially far apart. What happens to their electrostatic potential energy as they are brought closer together?

A closed system.If the piston is pulled upward so that it sits halfway between the position shown and the top of the cylinder, is the system still closed?

Consider the energy diagram shown in the figure .
You may want to reference (Pages 167 - 172) Section 5.2 while completing this problem. Does this diagram represent an increase or decrease in the internal energy of the system?

Consider the energy diagram shown in the figure .
You may want to reference (Pages 167 - 172) Section 5.2 while completing this problem. What sign is given to E for this process?

The contents of the closed box in each of the illustrations represent a system, and the arrows show the changes to the system during some process. The lengths of the arrows represent the relative magnitudes of q and w.
You may want to reference (Pages 167 - 172) Section 5.2 while completing this problem.For which process, if any, is there a net gain in internal energy?

Write an equation that expresses the first law of thermodynamics in terms of heat and work.

Under what conditions will the quantities q and w be negative numbers?

Consider a system consisting of two oppositely charged spheres hanging by strings and separated by a distance r1, as shown in the accompanying illustration. Suppose they are separated to a larger distance r2, by moving them apart along a track.
You may want to reference (Pages 167 - 172) Section 5.2 while completing this problem.What change, if any, has occurred in the potential energy of the system?

Consider a system consisting of two oppositely charged spheres hanging by strings and separated by a distance r1, as shown in the accompanying illustration. Suppose they are separated to a larger distance r2, by moving them apart along a track.
You may want to reference (Pages 167 - 172) Section 5.2 while completing this problem.What effect, if any, does this process have on the value of E?

Consider a system consisting of two oppositely charged spheres hanging by strings and separated by a distance r1, as shown in the accompanying illustration. Suppose they are separated to a larger distance r2, by moving them apart along a track.
You may want to reference (Pages 167 - 172) Section 5.2 while completing this problem.What can you say about q and w for this process?

The internal energy of an ideal gas depends only on its temperature.Explain.

Two identical refrigerators are plugged in for the first time. Refrigerator A is empty (except for air) and refrigerator B is filled with jugs of water. The compressors of both refrigerators immediately turn on and begin cooling the interiors of the refrigerators. After two hours, the compressor of refrigerator A turns off while the compressor of refrigerator B continues to run. The next day, the compressor of refrigerator A can be heard turning on and off every few minutes, while the compressor of refrigerator B turns off and on every hour or so (and stays on longer each time).Explain these observations.

What is meant by the term state function?

Give an example of a quantity that is a state function and one that is not.

Is the volume of the system a state function?

You may have noticed that when you compress the air in a bicycle pump, the body of the pump gets warmer.
You may want to reference (Pages 167 - 172) Section 5.2 while completing this problem.Assuming the pump and the air in it comprise the system, what is the sign of w when you compress the air?

You may have noticed that when you compress the air in a bicycle pump, the body of the pump gets warmer.
You may want to reference (Pages 167 - 172) Section 5.2 while completing this problem.What is the sign of q for this process?

The diagram shows four states of a system, each with different internal energy, E.
You may want to reference (Pages 167 - 172) Section 5.2 while completing this problem.Which of the states of the system has the greatest internal energy?

The diagram shows four states of a system, each with different internal energy, E.
You may want to reference (Pages 167 - 172) Section 5.2 while completing this problem.In terms of the E values, which are the two expressions for the difference in internal energy between State A
and State B?

The diagram shows four states of a system, each with different internal energy, E.
You may want to reference (Pages 167 - 172) Section 5.2 while completing this problem.Which expression(s) represent the difference in energy between State C
and State D?

The diagram shows four states of a system, each with different internal energy, E.
You may want to reference (Pages 167 - 172) Section 5.2 while completing this problem.Suppose there is another state of the system, State E, and that its energy relative to State A
is
E = E1 + E4. Where would State E
be on the diagram?

Why is the change in enthalpy usually easier to measure than the change in internal energy?

H is a state function, but q is not a state function. Explain.

A system that does work on its surroundings.If the amount of zinc used in the reaction is increased, will more work be done by the system? Is there additional information you need in order to answer this question?

If a system does not change its volume during the course of a process, does it do pressure-volume work?

What is work?

Suppose that the gas-phase reaction 2 (g) + O2 (g) 2 (g) were carried out in a constant-volume container at constant temperature.Would the measured heat change represent H or E?

What is a state function?

List some examples of state functions.

Sign conventions for heat and work. Heat, q, gained by a system and work, w, done on a system are both positive quantities, corresponding to "deposits" of internal energy into the system. Conversely, heat transferred from the system to the surroundings and work done by the system on the surroundings are both "withdrawals" of internal energy from the system.Suppose a system receives a “deposit” of 51
J of work from the surroundings and loses a “withdrawal” of 83
J of heat to the surroundings. What is the magnitude and the sign of E for this process?

Calculate E, if q =
0.766 kJ and w =
-840 J .

Calculate E, if a system releases 66.6 kJ of heat to its surroundings while the surroundings do 46.0 kJ of work on the system.

Calculate E, if the system absorbs 7.26 kJ of heat from the surroundings while its volume remains constant (assume that only exttip{P-V}{P-V} work can be done).

A gas is confined to a cylinder under constant atmospheric pressure, as illustrated in the following figure. When the gas undergoes a particular chemical reaction, it absorbs 826 J of heat from its surroundings and has 0.66 kJ of P-V work done on it by its surroundings.
What is the value of E for this process?

During a normal breath, our lungs expand about 0.50 L against an external pressure of 1.0 atm. How much work is involved in this process (in J)?

You may want to reference (Pages 177 - 178) Section 5.4 while completing this problem.How much work (in J) is involved in a chemical reaction if the volume decreases from 4.80 to 1.51
L against a constant pressure of 0.851
atm?

A 100-W lightbulb is placed in a cylinder equipped with a moveable piston. The lightbulb is turned on for 0.020 hour, and the assembly expands from an initial volume of 0.90 L to a final volume of 5.88 L against an external pressure of 1.0 atm.Calculate w.

A 100-W lightbulb is placed in a cylinder equipped with a moveable piston. The lightbulb is turned on for 0.020 hour, and the assembly expands from an initial volume of 0.90 L to a final volume of 5.88 L against an external pressure of 1.0 atm.Calculate q.

A sample of gas is contained in a cylinder-and-piston arrangement. It undergoes the change in state shown in the drawing. Assume first that the cylinder and piston are perfect thermal insulators that do not allow heat to be transferred.
What is the value of q for the state change?

A gas is confined to a cylinder under constant atmospheric pressure, as illustrated in the following figure. When the gas undergoes a particular chemical reaction, it absorbs 826 J of heat from its surroundings and has 0.66 kJ of P-V work done on it by its surroundings.
What is the value of H for this process?

Consider the accompanying energy diagram. (a) Does this diagram represent an increase or decrease in the internal energy of the system?

The contents of the closed box in each of the following illustrations represent a system, and the arrows show the changes to the system during some process. The lengths of the arrows represent the relative magnitudes of q and w. (a) Which of these processes is endothermic?

Which statement is true of the internal energy of a system and its surroundings during an energy exchange with a positive E system?The internal energy of the system and the surroundings is 0The internal energy of the system and surroundings increasesThe internal energy of the system decreases and the internal energy of the surroundings increasesThe internal energy of the system and surroundings decreaseThe internal energy of the system increases and the internal energy of the surroundings decreases

In the accompanying cylinder diagram a chemical process occurs at constant temperature and pressure. (a) Is the sign of w indicated by this change positive or negative?

Imagine a container placed in a tub of water, as depicted in the accompanying diagram. (a) If the contents of the container are the system and heat is able to flow through the container walls, what qualitative changes will occur in the temperatures of the system and in its surroundings? What is the sign of q associated with each change? From the system’s perspective, is the process exothermic or endothermic?

At constant pressure, which of these systems do work on the surroundings?
a. 2A(g) + 3B(g) → 4C(g)
b. A(s) + B(g) → 2C(g)
c. A(g) + B(g) → 3C(g)
d. A(s) + 2B(g) → C(g)
e. More than one of the above

Which statement is true of the internal energy of a system and its sorroundings during an energy exchange with a positive ΔEsys?A. The internal energy of the system decreases and the internal of the surroundings increases.B. The internal energy of the system increases and the internal energy of the surroundings decreases.C. The internal energy of both the system and the surroundings decreases.D. The internal energy of both system and the surroundings increases.

Which one of the following statements is FALSE?The first law of thermodynamics says that the energy lost by the system must be gained by the surroundings.A positive ΔH corresponds to an endothermic process.The enthalpy change for a reaction is independent of the state of the reactants and products.The change of internal energy is the sum of heat and workIf work is done by the system, the sign of work is negative

A sample of gas occupies a volume of 51.1 mL. As it expands, it does 137.7 J of work on its surroundings at a constant pressure of 783 torr.What is the final volume of the gas?

A rolling billiard ball collides with another billiard ball. That billiard ball (defined as the system) stops rolling after the collision. Identify the energy exchange and the sign of ΔE for the system.A. work; - ΔEB. work; + ΔEC. heat; - ΔED. heat; + ΔE

Suppose an Olympic diver who weighs 52.0 kg executes a straight dive from a 10-m platform. At the apex of the dive, the diver is 10.8 m above the surface of the water. (c) Does the diver do work on entering the water? Explain.

All of the following statements are true EXCEPT:a. energy is a state property.b. the magnitude of delta H is proportional to the limiting reagent.c. the magnitude of delta H for a reaction is equivalent to that of the reverse reaction.d. the magnitude of delta H is proportional to the amount of product produced.e. the magnitude of delta H is dependent upon the intermediate steps in the chemical reaction.

(b) An adult person radiates heat to the surroundings at about the same rate as a 100-watt electric incandescent lightbulb. What is the total amount of energy in kcal radiated to the surroundings by an adult in 24 h?

Limestone stalactites and stalagmites are formed in caves by the following reaction:Ca2+ (aq) + 2 HCO3– (aq) → CaCO3 (s) + CO2 (g) + H2O (l)If 1 mol of CaCO3 forms at 298 K under 1 atm pressure, the reaction performs 2.47 kJ of P-V work, pushing back the atmosphere as the gaseous CO2 forms. At the same time, 38.95 kJ of heat is absorbed from the environment. What are the values of ΔH and of ΔE for this reaction?

A gas is allowed to expand at constant temperature from a volume of 2.0 L to 11.2 L against an external pressure of 0.750 atm. If the gas absorbs 128 J of heat from the surroundings, what are the values of q, w, and ΔE respectively?
a. 128 J, 6.9 J, 135 J
b. 128 J, -6.9 J, 121 J
c. 128 J, 697 J, 825 J
d. 128 J, -697 J, -569 J
e. -128 J, -6.9 J, -135 J

For the following processes, calculate the change in internal energy of the system and determine whether the process is endothermic or exothermic: (a) A balloon is heated by adding 850 J of heat. It expands, doing 382 J of work on the atmosphere.

For the following processes, calculate the change in internal energy of the system and determine whether the process is endothermic or exothermic: (b) A 50-g sample of water is cooled from 30°C to 15°C, thereby losing approximately 3140 J of heat.

For the following processes, calculate the change in internal energy of the system and determine whether the process is endothermic or exothermic: (c) A chemical reaction releases 6.47 kJ of heat and does no work on the surroundings.

A balloon is inflated from 0.0100 L to 0.400 L against an external pressure of 10.00 atm. How much work is done in joules? (101.3 J = 1 L. atm)a. -395 Jb. -0.395 Jc. -39.5 Jd. 39.5 Je. 0.395 J

Which set of signs for q and w represent a system that is doing work on the surroundings and losing heat to the surroundings?a) -q, -wb) +q, +wc) -q, +wd) +q, -we) None of these represent the system referenced above.

A typical breath is around 0.5 L, but to get 2 sig figs, let’s assume you breathe in 0.48 L. How much work is done when you exhale against an atmosphere pressure of 750 mmHg? Be sure to include a + or - sign in your answer.

A system that does no work but which receives heat from the surroundings has:
a) q < 0, ΔE > 0
b) q > 0, ΔE < 0
c) q = ΔE
d) q = -ΔE
e) w = ΔE

Consider an ideal gas enclosed in a 1.00 L container at an internal pressure of 10.0 atm.Calculate the work, w, if the gas expands against a constant external pressure of 1.00 atm to a final volume of 25.0 L. Now calculate the work done if this process is carried out in two steps.1. First, let the gas expand against a constant external pressure of 5.00 atm to a volume of 5.00 L.2. From there, let the gas expand to 25.0 L against a constant external pressure of 1.00 atm.

A process is carried out on a system at constant external pressure. During the process 150. J of heat moves from the surroundings to the system, and the system expands, performing 400.J of work. The values for q, w, ΔU, and ΔH for the process are:a. q = -150.J, w = 400.J, ΔU = 250.J, ΔH = -150.Jb. q = 150.J, w = 400.J, ΔU = 550.J, ΔH = 550.Jc. q = 150.J, w = 400.J, ΔU = 550.J, ΔH = 150.Jd. q = 150.J, w = -400.J, ΔU = -250.J, ΔH = -250.Je. q = 150.J, w = -400.J, ΔU = -250.J, ΔH = 150.J

Consider an ideal gas enclosed in a 1.00 L container at an internal pressure of 10.0 atm. Calculate the work, w, if the gas expands against a constant external pressure of 1.00 atm to a final volume of 10.0 L.

The heat of vaporization of water at 373 K is 40.7 kJ/mol. Find q, w, ΔE, and ΔH for the evaporation of 454 g of water at this temperature.

Which expression describes the heat evolved in a chemical reaction when the reaction is carried out at constant pressure? Explain.a. ∆E – wb. ∆Ec. ∆E – q

When 1 mol of a gas burns at constant pressure, it produces 2418 J of heat and does 51 of work. Identify ∆E, ∆H, q, and w for the process.

Which statement is true of a reaction in which ∆V is positive? Explain. a. ∆H = ∆Eb. ∆H > ∆Ec. ∆H < ∆E

At constant pressure, which of these systems do work on the surroundings?
A. 2A(g) + 3B(g) → 4C(g)
B. A(s) + B(s) → C(g)
C. 2A(g) + 2B(g) → 3C(g)
D. 2A(g) +B(g) → 4C(g)
E. More than one of the above

Which is true when a gas expands isothermically against a constant pressure of two atmosphere (mark all that apply)?a. The system does not work.b. The gas releases heat.c. Heat is absorbed by the gas.d. The temperature of the gas decreases.e. No heat flows.

What is the change in the internal energy (in J) of a system that releases 1000 J of heat and does 225 J of work on the surroundings?a. -10,155b. -1225c. -775d. 775e. 1225

If the volume of a system increases from 10.0 L to 14.5 L against a constant external pressure of 1.00 atm, and absorbs 655 J of heat, what is the change in internal energy of the system (∆Esys)? (1 L∙atm = 101.3 J)A) 199 JB) 1111 JC) 651 JD) −1111 JE) −199 J

A certain liquid has Δvap Ho = 26.0 kJmol -1. Calculate q, w, ΔU, and ΔH when 0.50 mol is vaporized at 250K and 750 Torr.

Which one of the following thermodynamic quantities is not a state function?a) workb) enthalpyc) entropyd) internal energye) free energy

A gas at 25.00°C and 360.00 torr (760 torr = 1atm) expands from 25.0 L to 35.0 L. What is the value of the work done on or by the gas? (1 L•atm = 101.325 J) a. 480 Jb. 3600 Jc. -3600 Jd. 1013.25 Je. -480 J

Which set of signs for q and w represent a system that is doing work on the surroundings and losing heat to surroundings?a. – q, -wb. + q, +wc. – q, +wd. + q, -we. None of these represent the system referenced above.

When fuel is burned in a cylinder equipped with a piston, the volume expands from 0.255 L to 1.45 L against an external pressure of 1.02 atm. In addition, 875 J is emitted as heat. What is the ∆E? (101.3 J = 1 L • atm)

Heat absorbed by a system at constant volume is equal to1. ∆G2. ∆S3. ∆H4. ∆V5. ∆E

Which of the following statements concerning the first law of thermodynamics is/are true?I) The internal energy of the universe is always increasing.II) Internal energy lost by a system is always gained by surroundings.III) The universe is an isolated system.1. II and III only2. III only3. I and II only4. II only5. I and III only6. I, II and III7. I only

Heat is1) A measure of temperature.2) A measure of the change in temperature.3) A measure of thermal energy.4) A measure of thermal energy transferred between two bodies at different temperatures.5) All of the above.

A gas is allowed to expand, at a constant temperature, from a volume of 1.0 L to 10.1 L against an external pressure of 0.50 atm. If the gas absorbs 250 J of heat from the surroundings, what are the values of q, w, and ∆E?

Which of the following depicts a situation where the least amount of work is done by a sample of gas? [1 atm = 101325 Pa]a) A 20-L sample of gas expands to 500 L against a vacuumb) A 1-L sample of gas expands to 30 L against a pressure of 2.22 atmc) A 1-L sample of gas expands to 30 L against a pressure of 2.22 Pad) A 20-L sample of gas expands to 500 L against a pressure of 30 atme) Two or more are tied

Calculate the amount of work done when 2.5 mole of H 2O vaporizes at 1.0 atm and 25°C. Assume the volume of liquid H2O is negligible compared to that of vapor. (1 L atm = 101.3 J)1) -61.9 J2) -6.19 kJ3) 61.9 J4) 5.66 kJ5) 518 J

Which statement is always true of the internal energy of a system and its surroundings during an energy exchange with an endothermic value of ΔUsystem?a) ΔHsurroundings > 0b) The internal energy of the system and surroundings increase togetherc) The internal energy of the system decreases while the internal energy of the surroundings increasesd) The internal energy of the system and surroundings decrease togethere) The internal energy of the system increases while the internal energy of the surroundings decreases

The internal energy of a system is the sum of all of its ___.A. thermal energy and kinetic energyB. potential energy and chemical energyC. thermal energy and chemical energyD. potential energy and kinetic energy

Calculate the work for the expansion of CO2 from 1.0 to 3.0 liters against a pressure of 1.0 atm at constant temperature.

Oxygen gas at 34.5°C is compressed from 45.7 L to 34.5 L against a constant pressure of 0.987 atm. If the oxygen gas is defined as the system, how much work is done (in J) on the system? (1 L atm = 101.3 J)A. 1.12 × 103 JB. −1.11 × 101 JC. 1.11 × 101 JD. −4.55 × 103 JE. −1.12 × 103 J

A system absorbs 159 kJ of heat, and performs 84 kJ of work on the surroundings. What is ΔE of the system?

An ideal gaseous reaction (which is a hypothetical gaseous reaction that conforms to the laws governing gas behavior) occurs at constant pressure of 30.0 atm and releases 67.9 kJ of heat. Before the reaction, the volume of the system was 8.00 L. After the reaction, the volume of the system was 2.80 L.Calculate the total internal energy change, ΔE, in kilo joules.

Which of the following is not a state function?A. PressureB. ConcentrationC. Internal energyD. Work

If energy flows into a chemical system and out of the surroundings, what is the sign of ΔEsystem?

If the internal energy of the products of a reaction is higher than the internal energy of the reactants, what is the sign of ΔE for the reaction?

In which of these cases do the surroundings do work on the system?a. q = -47 kJ, w = +88 kJb. q = +82 kJ, w = -47 kJc. q = +47 kJ, w = 0

During an energy exchange, a chemical system absorbs energy from its surroundings. What is the sign of ΔEsys for this process?

A balloonist begins a trip in a helium-filled balloon in early morning when the temperature is 15°C. By mid-afternoon, the temperature is 30.°C. Assuming the pressure remains at 1.00 atm, for each mole of helium, explain the relationship between the heat (q) transferred (in J) and ΔH for the process (in J).

Three gas-phase reactions were run in a constant-pressure piston apparatus as shown in the following illustration. For each reaction, give the balanced reaction and predict the sign of w (the work done) for the reaction.If just the balanced reactions were given, how could you predict the sign of w for a reaction?

Three gas-phase reactions were run in a constant-pressure piston apparatus as shown in the following illustration. For each reaction, give the balanced reaction and predict the sign of w (the work done) for the reaction.If just the balanced reactions were given, how could you predict the sign of w for a reaction?

Three gas-phase reactions were run in a constant-pressure piston apparatus as shown in the following illustration. For each reaction, give the balanced reaction and predict the sign of w (the work done) for the reaction.If just the balanced reactions were given, how could you predict the sign of w for a reaction?

You may want to reference (Pages 253 - 258) Section 6.3 while completing this problem.Identify each energy exchange as primarily heat or work.a. A rolling billiard ball collides with another billiard ball. The first billiard ball (defined as the system) stops rolling after the collision.b. A book falls to the floor. (The book is the system).c. A father pushes his daughter on a swing. (The daughter and the swing are the system).

You may want to reference (Pages 253 - 258) Section 6.3 while completing this problem.Determine whether the sign of E is positive or negative for the system.a. A rolling billiard ball collides with another billiard ball. The first billiard ball (defined as the system) stops rolling after the collision.b. A book falls to the floor. (The book is the system).c. A father pushes his daughter on a swing. (The daughter and the swing are the system).

Consider the accompanying diagram. Ball A is allowed to fall and strike ball B. Assume that all of ball A’s energy is transferred to ball B at point I, and that there is no loss of energy to other sources. What is the kinetic energy and the potential energy of ball B at point II? The potential energy is given by PE = mgz, where m is the mass in kilograms, g is the gravitational constant (9.81 m/s2), and z is the distance in meters.

The oxidation of copper(I) oxide, Cu 2O(s), to copper(II) oxide, CuO(s), is an exothermic process.
2CuO2(s) + O2(g) → 4CuO(s)
The change in enthalpy upon reaction of 67.68 g of CuO (s) is -69.06 kJ
Calculate the work, w, and the energy change, ΔU rxn, when 67.68 g of Cu 2O (s) is oxidized at constant pressure of 1.00 bar and at constant temperature of 25°C?

Classify the following by the sign of delta U for the system: the following can be classified into these three categories (negative,positive, not enough data)1. The system contracts and the surroundings get cooler.2. The system expands and the surroundings get cooler.3. The system contracts and the surroundings get hotter.4. The system expands and the surroundings get hotter.

A gas absorbs 45 kJ of heat and does 29 kJ of work. Calculate ΔE.

A system releases 125 kJ of heat while 104 kJ of work is done on it. Calculate ΔE.

When organic matter decomposes under oxygen-free (anaerobic) conditions, methane is one of the products. Thus, enormous deposits of natural gas, which is almost entirely methane, serve as a major source of fuel for home and industry.Known deposits of natural gas can produce 5600 EJ of energy (1 EJ = 10 18 J). Current total global energy usage is 4.0 x 102 EJ per year. Find the mass (in kg) of known deposits of natural gas (ΔH°rxn for the combustion of CH4 = −802 kJ/mol).

Calculate ΔE for each of the followinga. q = -47 kJ, w = +88 kJ

You may want to reference (Pages 259 - 264) Section 6.4 while completing this problem.When fuel is burned in a cylinder equipped with a piston, the volume expands from 0.255 L to 1.360 L against an external pressure of 1.02 atm. In addition, 851 J is emitted as heat. What is ΔE for the burning of the fuel?

Calculate ΔE for each of the following:b. q = +82 kJ, w = -47 kJ

You may want to reference (Pages 253 - 258) Section 6.3 while completing this problem.A cylinder and piston assembly (defined as the system) is warmed by an external flame. The contents of the cylinder expand, doing work on the surroundings by pushing the piston outward against the external pressure. If the system absorbs 545 J of heat and does 488 J of work during the expansion, what is the value of ΔE?

Calculate ΔE for each of the followingc. q = +47 kJ, w = 0

A system undergoes a process consisting of the following two steps: Step 1: The system absorbs 72 J of heat while 35 J of work is done on it. Step 2: The system absorbs 35 J of heat while performing 72 J of work.Calculate ΔE for the overall process.

If the internal energy of a thermodynamic system is increased by 300. J while 75 J of expansion work is done, how much heat was transferred and in which direction, to or from the system?

A system releases 651 kJ of heat and does 130 kJ of work on the surroundings. What is the change in internal energy of the system?

The gas in a piston (defined as the system) is warmed and absorbs 660 J of heat. The expansion performs 346 J of work on the surroundings. What is the change in internal energy for the system?

The air within a piston equipped with a cylinder absorbs 565 J of heat and expands from an initial volume of 0.12 L to a final volume of 0.86 L against an external pressure of 1.0 atm. What is the change in internal energy of the air within the piston?

When 1 mol of a fuel is burned at constant pressure, it produces 3453 kJ of heat and does 12 kJ of work. What is the value of ΔE for the combustion of the fuel?

When 1 mol of a fuel is burned at constant pressure, it produces 3453 kJ of heat and does 12 kJ of work. What is the value of ΔH for the combustion of the fuel?

Calculate the internal energy change for each of the following. A piston is compressed from a volume of 8.30 L to 2.80 L against a constant pressure of 1.90 atm. In the process, there is a heat gain by the system of 350. J.

Calculate the internal energy change for each of the following.One hundred (100.) joules of work is required to compress a gas. At the same time, the gas releases 23 J of heat.

Calculate the internal energy change for each of the following.A piston expands against 1.00 atm of pressure from 11.2 L to 29.1 L. In the process, 1037 J of heat is absorbed.

A system receives 425 J of heat from and delivers 425 J of work to its surroundings. What is the change in internal energy of the system (in J)?

A system releases 255 cal of heat to the surroundings and delivers 428 cal of work. What is the change in internal energy of the system (in cal)?

What is the change in internal energy (in J) of a system that releases 675 J of thermal energy to its surroundings and has 530 cal of work done on it?

What is the change in internal energy (in J) of a system that absorbs 0.615 kJ of heat from its surroundings and has 0.247 kcal of work done on it?

A balloonist begins a trip in a helium-filled balloon in early morning when the temperature is 15°C. By mid-afternoon, the temperature is 30.°C. Assuming the pressure remains at 1.00 atm, for each mole of helium, calculate the change in internal energy, ΔE (Hint: Helium behaves like an ideal gas, so E = 3/2nRT. Be sure the units of R are consistent with those of E.)

A balloon filled with 39.1 moles of helium has a volume of 876 L at 0.0°C and 1.00 atm pressure. The temperature of the balloon is increased to 38.0°C as it expands to a volume of 998 L, the pressure remaining constant. Calculate q, w, and ΔE for the helium in the balloon. (The molar heat capacity for helium gas is 20.8 J/°C • mol.)

A 100-W lightbulb is placed in a cylinder equipped with a moveable piston. The lightbulb is turned on for 0.020 hour, and the assembly expands from an initial volume of 0.90 L to a final volume of 5.88 L against an external pressure of 1.0 atm. Use the wattage of the lightbulb and the time it is on to calculate ΔE in joules (assume that the cylinder and lightbulb assembly is the system and assume two significant figures).

One mole of H2O(g) at 1.00 atm and 100.°C occupies a volume of 30.6 L. When 1 mole of H2O(g) is condensed to 1 mole of H2O(l) at 1.00 atm and 100.°C, 40.66 kJ of heat is released. If the density of H2O(l) at this temperature and pressure is 0.996 g/cm3, calculate ΔE for the condensation of 1 mole of water at 1.00 atm and 100.°C.

A 21.0-L volume of an ideal gas in a cylinder with a piston is at a pressure of 3.2 atm. Enough weight is suddenly removed from the piston to lower the external pressure to 1.6 atm. The gas then expands at constant temperature until its pressure is 1.6 atm. Find ΔE for this change in state.

A 21.0-L volume of an ideal gas in a cylinder with a piston is at a pressure of 3.2 atm. Enough weight is suddenly removed from the piston to lower the external pressure to 1.6 atm. The gas then expands at constant temperature until its pressure is 1.6 atm. Find ΔH for this change in state.

Consider a balloon filled with helium at the following conditions.313 g He 1.00 atm 1910. L Molar Heat Capacity = 20.8 J/°C • molThe temperature of this balloon is decreased by 41.6°C as the volume decreases to 1643 L, with the pressure remaining constant. Determine q, w, and ΔE (in kJ) for the compression of the balloon.

When 1 mol of a gas burns at constant pressure, it produces 2422 J of heat and does 6 kJ of work.Identify ΔE for the process.

When 1 mol of a gas burns at constant pressure, it produces 2422 J of heat and does 6 kJ of work.Identify ΔH for the process.

You may want to reference (Page 256) Section 6.3 while completing this problem.A chemical system produces 155 kJ of heat and does 23 kJ of work. What is ΔE for the surroundings?

Isooctane (C8H18; d = 0.692 g/mL) is used as the fuel in a test of a new automobile drive train.How much energy (in kJ) is released by combustion of 20.4 gal of isooctane to gases (ΔH°rxn = −5.44 x 103 kJ/mol)?

Lighters are usually fueled by butane (C4H10). When 1 mole of butane burns at constant pressure, it produces 2658 kJ of heat and does 3 kJ of work. What is the value of ΔH for the combustion of one mole of butane?

Lighters are usually fueled by butane (C4H10). When 1 mole of butane burns at constant pressure, it produces 2658 kJ of heat and does 3 kJ of work.What is the value of ΔE for the combustion of one mole of butane?

You may want to reference (Pages 253 - 258)section 6.3 while completing this problem.A system absorbs 192 kJ of heat and the surroundings do 120 kJ of work on the system. What is the change in internal energy of the system?

You may want to reference (Pages 253 - 258) Section 6.3 while completing this problem.The air in an inflated balloon (defined as the system) is warmed over a toaster and absorbs 125 J of heat. As it expands, it does 78 kJ of work. What is the change in internal energy for the system?

You may want to reference (Pages 265 - 266) Section 6.5 while completing this problem.A gas is compressed from an initial volume of 5.60 L to a final volume of 1.23 L by an external pressure of 1.00 atm. During the compression the gas releases 125 J of heat. What is the change in internal energy of the gas?

Consider the following cyclic process carried out in two steps on a gas: Step 1: 45 J of heat is added to the gas, and 10. J of expansion work is performed. Step 2: 60. J of heat is removed from the gas as the gas is compressed back to the initial state. Calculate the work for the gas compression in Step 2.

You may want to reference (Pages 259 - 264) Section 6.4 while completing this problem.A cylinder equipped with a piston expands against an external pressure of 1.51 atm. If the initial volume is 0.505 L and the final volume is 1.280 L, how much work (in J) is done?

How much work (in J) is required to expand the volume of a pump from 0.0 L to 2.5 L against an external pressure of 1.2 atm?

You may want to reference (Pages 259 - 264) Section 6.4 while completing this problem.During a breath, the average human lung expands by about 0.50 L. If this expansion occurs against an external pressure of 1.0 atm, how much work (in joules) is done during the expansion?

A sample of an ideal gas at 15.0 atm and 10.0 L is allowed to expand against a constant external pressure of 2.00 atm to a volume of 75.0 L. Calculate the work in units of kJ for the gas expansion.

A balloonist begins a trip in a helium-filled balloon in early morning when the temperature is 15°C. By mid-afternoon, the temperature is 30.°C. Assuming the pressure remains at 1.00 atm, for each mole of helium, calculate the initial and final volumes.

A piston performs work of 210. L ? atm on the surroundings, while the cylinder in which it is placed expands from 10. L to 25 L. At the same time, 45 J of heat is transferred from the surroundings to the system. Against what pressure was the piston working?

Consider a mixture of air and gasoline vapor in a cylinder with a piston. The original volume is 40. cm3. If the combustion of this mixture releases 950. J of energy, to what volume will the gases expand against a constant pressure of 650. torr if all the energy of combustion is converted into work to push back the piston?

A balloonist begins a trip in a helium-filled balloon in early morning when the temperature is 15°C. By mid-afternoon, the temperature is 30.°C. Assuming the pressure remains at 1.00 atm, for each mole of helium, calculate the work (w) done by the helium (in J).

A balloonist begins a trip in a helium-filled balloon in early morning when the temperature is 15°C. By mid-afternoon, the temperature is 30.°C. Assuming the pressure remains at 1.00 atm, for each mole of helium, calculate the heat (q) transferred (in J).

As a system increases in volume, it absorbs 52.5 J of energy in the form of heat from the surroundings. The piston is working against a pressure of 0.500 atm. The final volume of the system is 58.0 L. What was the initial volume of the system if the internal energy of the system decreased by 102.5 J?

One mole of nitrogen gas confined within a cylinder by a piston is heated from 0°C to 819°C at 1.00 atm.a) Calculate the work done by the expanding gas in joules (1 J = 9.87 x 10 −3 atm•L). Assume that all the energy is used to do work.

At constant temperature, a sample of helium gas expands from 922 mL to 1.14 L against a pressure of 2.33 atm. Find w (in J) done by the gas (101.3 J = 1 atm•L).

The external pressure on a gas sample is 2660 mmHg, and the volume changes from 0.88 L to 0.63 L at constant temperature. Find w (in kJ) done on the gas (1 atm•L = 101.3 J).

A 21.0-L volume of an ideal gas in a cylinder with a piston is at a pressure of 3.2 atm. Enough weight is suddenly removed from the piston to lower the external pressure to 1.6 atm. The gas then expands at constant temperature until its pressure is 1.6 atm. Find q for this change in state.

A 21.0-L volume of an ideal gas in a cylinder with a piston is at a pressure of 3.2 atm. Enough weight is suddenly removed from the piston to lower the external pressure to 1.6 atm. The gas then expands at constant temperature until its pressure is 1.6 atm. Find w for this change in state.

An amount of an ideal gas expands from 12.1 L to 24.1 L at a constant pressure of 1.0 atm. Then the gas is cooled at a constant volume of 24.1 L back to its original temperature. Then it contracts back at a constant temperature to its original volume. Find the total heat flow for the entire process.

When 1 mol of a gas burns at constant pressure, it produces 2422 J of heat and does 6 kJ of work. Identify q for the process.

When 1 mol of a gas burns at constant pressure, it produces 2422 J of heat and does 6 kJ of work. Identify w for the process.

You may want to reference (Page 262) Section 6.4 while completing this problem.A cylinder with a moving piston expands from an initial volume of 0.250 L against an external pressure of 2.10 atm. The expansion does 276 J of work on the surroundings. What is the final volume of the cylinder?

Isooctane (C8H18; d = 0.692 g/mL) is used as the fuel in a test of a new automobile drive train.The energy delivered to the automobile’s wheels at 65 mph is 5.5 x 10 4 kJ/h. Assuming all the energy is transferred as work to the wheels, how far (in km) can the vehicle travel on the 20.4 gal of fuel?

You may want to reference (Pages 267 - 270) Section 6.6 while completing this problem.The change in internal energy for the combustion of 1.0 mol of octane at a pressure of 1.0 atm is -5084.3 kJ. If the change in enthalpy is -5074.2 kJ, how much work is done during the combustion?

A Carnot engine receives 280 kW of heat from a heat-source reservoir at 500ºC and rejects heat to a heat-sink reservoir at 25ºC. What are the power developed and the heat rejected?

An expanding gas does 173 J of work on its surroundings at a constant pressure of 1.01 atm. If the gas initially occupied 68.0mL, what is the final volume of the gas?

Enter your answer in the rpovided box.In a gas expansion, 71 J of heat is absorbed by the system, and the energy of the system decreases by 124 J. Calculate the work done.

Use the data from this table of thermodynamic properties to calculate the maximum amount of work that can be obtained from the combustion of 1.00 mole of ethane, CH3CH3(g) at 25 "C and standard conditions.

Calculate the work associated with the compression of a gas from 121.0 L to 80.0 L at a constant pressure of 16.7 atm.

What is the change in internal energy (in kJ) when a gas does 135 J of work on the surroundings and at the same time absorbs 156 J of heat? a. 0.021 kJ b. 21 kJ c. -0.291 kJ d. 0.291 kJ e. 0.458 kJ

One mole of an ideal gas is expanded from a volume of 1.00 liter to a volume of 8.41 liters against a constant external pressure of 1.00 atm. How much work (in joules) is performed on the surroundings? Ignore significant figures for this problem. (T= 300 K: 1 L•atm = 101.3 J) A. 375 J B. 751 J C. 225 times 103 J D. 852 J E. none of these

A piston has an external pressure of 5.00 atm. How much work has been done in joules if the cylinder goes from a volume of 0.180 liters to 0.530 liters? Express your answer with the appropriate units.

Automobile airbags contain solid sodium azide, NaN3, that reacts to produce nitrogen gas when heated, thus inflating the bag.Calculate the value of work, w, for the following system if 14.2g of NaN3 reacts completely at 1.00 atm and 22℃.

Classify each of the following as a path function or a state function.i) Workii) Energyiii) Distance travelediv) Enthalpyv) Heat

At constant pressure, which of these systems do work on the surroundings? Check all that apply.a. 2A(g)+3B(g) --> 4C(g)b. A(s)+B(g) --> 2C(g)c. A(g)+B(g) --> 3C(g)d. A(s)+2B(g) --> C(g)