**Graham's Law** states that the rate of effusion of a gas is inversely proportional to the square root of its molar mass.

**Effusion** involves a gas escaping a container through an opening.

Concept #1: Understanding Graham's Law of Effusion.

When comparing the **rate or speed of two gases** then we must use **Graham’s Law of Effusion**.

Example #1: Calculate the ratio of the effusion rates of helium and methane (CH_{4}).

The gas named first will represent gas 1 and the second gas will represent gas 2. Once that is established we simply use Graham’s Law of Effusion.

Example #2: Rank the following in order of increasing rate of effusion:

O_{2} AlF_{5} CO_{2} Xe

Calculate the ratio of effusion rates for Ar and Kr.

A sample of neon effuses from a container in 76 seconds. The same amount of an unknown noble gas requires 155 seconds. Identify the gas.

A sample of N2O effuses from a container in 42 seconds. How long would it take the same amount of gaseous I2 to effuse from the same container under identical conditions?

The graph shows the distribution of molecular velocities for two different molecules (A and B) at the same temperature. Which molecule has the higher molar mass? Which molecule would have the higher rate of effusion?

At a given temperature and pressure, a sample of Gas A is observed to diffuse twice as fast as a sample of a different gas, B. Based on this:
A. The molar mass of A is one fourth that of B
B. The molar mass of A is one half that of B
C. The molar mass of A is 0.707 times that of B
D. The molar mass of A is 1.414 times that of B
E. The molar mass of A is four times that of B

How many times faster will He gas pass through a pin hole than SO2 gas?
a) 4
b) 1/4
c) 16
d) 1/16
e) none of the given answers

Using Graham's Law of effusion, calculate the ratio of the effusion rates of H 2 to CO through a pinhole.

An unknown gas Q diffuses at a RATE 1.65 times faster than that of propane, C 3H8. Which of these are most likely to be Q?
a. He
b. Ne
c. H2O
d. CH4
e. O2

The mass particle is 10% larger than that of particle B. If particle B travels 100 m during effusion, how far would particle A travel during effusion?
a) 90 m
b) 95 m
c) 100 m
d) 105 m
e) 110 m

Exactly 10 mL, of gas A (MM = 15.0 g/mol) effuse through an opening in 2.0 sec. Exactly 10 mL of gas B effuse through the same opening in 8.0 sec. What is the molar mass of gas B?
a) 60 g/mol
b) 480 g/mol
c) 240 g/mol
d) 120 g/mol

A sample of N2 gas is contaminated with a gas (A) of unknown molar mass. The partial pressure of each gas is known to be 200 Torr at 25°C. The gases are allowed to effuse through a pinhole, and it is found that gas A escapes at three times the rate of N2. The molar mass of gas A is:
a) 3.11
b) 252
c) 84.0
d) 9.33
e) none of these

Second-hand smoke consist of many molecules including nicotine. How much faster or slower does the nicotine diffuse, compared to carbon dioxide? (MW nicotine = 160g/mol)
1. About half as fast
2. As gases, the two molecules diffuse at the same rate
3. About 4 times faster
4. About a fourth as fast
5. About twice as fast

The gas for which instance will effuse faster?

Oxygen gas effuses at a rate that is 1.49 times that of an unknown gas (at the same temperature). What is the identity of the unknown gas?
A) Ar
B) HBr
C) SO2
D) Cl2
E) He

The mass of particle A is 10% larger than that of particle B. If particle B travels 100m during effusion, how far would particle A travel during effusion?
a. 90 m
b. 95 m
c. 100 m
d. 105 m
e. 110 m

At a particular temperature and pressure, it takes 4.55 min for a 1.5 L sample of He to effuse through a porous membrane. How long would it take for a 1.5 L of F2 to effuse under the same conditions?
a. 18 min
b. 14 min
c. 10 min
d. 5 min
e. 1.5 min

A sample of helium effuses through a porous container 7.70 times faster than does unknown gas X. What is the molar mass of the unknown gas?
1. 129.96
2. 153.76
3. 169.0
4. 112.36
5. 190.44
6. 237.16
7. 275.56
8. 392.04
9. 201.64
10. 368.64

At any given temperature, how much more quickly will He effuse than Xe?
1. 5.7 times more quickly
2. .03 times more quickly
3. 8.1 times more quickly
4. They will diffuse at the same rate
5. 0.12 times more quickly
6. 32.8 times more quickly

Carbon dioxide effuses through a pinhole at a rate of 0.232 ml/min at 25.0 °C. Another gas effuses at a rate of 0.363 ml/min. What is the molar mass of the gas?

NO2 gas effuses ________times faster than Cl 2 gas.
a. 1.54
b. 0.649
c. 1.24
d. 0.770
e. 2.37

Consider the chemical reaction: 2 SO2 (g) → SO(g) + SO3 (g)
Determine if the sentence below is true or false
Between the two products, SO3 would have the highest rate of effusion.

The rate of effusion of oxygen to an unknown gas is 0.935. What is the other gas?
A) Ar
B) F2
C) Ne
D) N2

Consider a 1.0-L sample of helium gas and a 1.0-L sample of argon gas, both at room temperature and atmospheric pressure.
d. Which gas sample would have the faster rate of effusion?

A flask at room temperature contains exactly equal amounts (in moles) of nitrogen and xenon.
d. If a small hole were opened in the flask, which gas would effuse more quickly?

Rank from the highest to lowest effusion rate. To rank items as equivalent, overlap them.
H2, Ar, Ne, C4H8, CO

Given the gases Ne, He, H2, Kr, put them in order of their INCREASING rate of effusion.
1. Kr < Ne < He < H 2
2. H2 < He < Ne < Kr
3. He < H2 < Kr < Ne
4. Ne < Kr < H 2 < He

The rate of effusion of oxygen to an unknown gas is 0.935. What is the other gas?

The rate of effusion of two different gases is known asA) Avogadro's Law B) Graham's Law C) Charles's Law D) Boyle's LawE) Dalton's Law

Calculate the ratio of effusion rates of Cl2 to F2.

Calculate the ratio of effusion rates for Ar and Kr.

Calculate the ratio of effusion rates for Ar and Kr.

Consider two 1-L samples of gas, one H2 and one O2, both at 1 atm and 25°C. Compare the samples in terms of the characteristics listed. time for a given fraction of O2 molecules to effuse____time for a given fraction of H2 molecules to effuse a. is greater thanb. is less than c. is equal to d. is unrelated to e. None of these

The rate of effusion of SO2 gas through a porous barrier is observed to be 5.29 x 10-4 mol/h. Under the same conditions, the rate of effusion of NO2 gas would be mol/h.

A sample of O3 gas is observed to effuse through a pourous barrier in 1.07 minutes. Under the same conditions, the same number of moles of an unknown gas requires 1.44 minutes to effuse through the same barrier. The molar mass of the unknown gas is ___________ g/mol.

A sample of Br2(g) takes 34.0 min to effuse through a membrane. How long would it take the same number of moles of Ar(g) to effuse through the same membrane?

The effusion rate of A gas molecules will be twice higher than one of B gas molecules when B molar mass is ____ higher than A molar mass. (a) None of the above (b) 4 times (c) 3 times (d) 2 times

If 250 mL of methane, CH4, effuses through a small hole in 28 s, the time required for the same volume of helium to pass through the hole under the same conditions will be Selected Answer:Correct Answer:

The rate of effusion of SO2 gas through a porous barrier is observed to be 7.01 x 10-4 mol/h. Under the same conditions, the rate of effusion of CH4 gas would be __________ mol/h.

The rate of effusion of Xe gas through a porous barrier is to be 7.31 x 10-4 mol/h. Under the same conditions, the rate of effusion of O2 gas would be __________ mol/h.

A sample of CH4 gas is observed to effuse through a porous barrier in 5.53 minutes. Under the same conditions, the same number of moles of an unknown gas requires 7.07 minutes to effuse through the same barrier. The molar mass of the unknown gas is g/mol.

The rate of effusion of CH4 gas through a porous barrier is observed to be 5.48 x 10-4 mol/h. Under the same condition, the rate of effusion of Xe gas would be ____ mol/h.

The average molecular speed in a sample of O3 gas at a certain temperature is 386 m/s. The average molecular speed in a sample of Ar gas is temperature.

How much faster do ammonia (NH 3) molecules effuse than carbon monoxide (CO) molecules?Enter the ratio of the rates of effusion. Express your answer numerically using three significant figures.