Solution Chemistry

Solution Chemistry involves combining the concepts of molarity and stoichiometry

Molarity and Chemical Reactions

Concept: Under solution chemistry our given information may be in units of massvolume or molarity

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Stoichiometry is used when given the known quantity of one compound and asked the find the unknown quantity of another compound or element. Now we throw molarity into the mix. 

Concept: When dealing with solution chemistry we use a new adjusted stoichiometric chart. 

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Video Transcript

We already looked at a stoichiometric chart, this one is a new stoichiometric chart and we use this anytime we're doing stoichiometry and molarity is involved. So just like before, we're going to say that entities means atoms, molecules or particles. Just like before, we're going to be given information, so we're going to have given information. That given information will help us find unknown information.
In this case, because we're dealing with molarity, that's going to introduce a new unknown - volume. Here when we say volume, volume could be milliliters, it could be liters, it could even be microliters. The base, of course, will be liters.
Now, how do we go from volume of given to moles of given? To do that, all you have to remember is liters times molarity will give us these moles. Remember, we say that liters times molarity represents a complete set. So instead of giving us the moles of a compound, they could say we have 25 mL of a certain molarity of a compound. That's the same thing as saying I have that many moles of that same compound.
From this, remember we can go from moles of given to moles of unknown by doing a mole to mole comparison, just like in the last stoichiometric chart. If you know moles of unknown, you can find entities of unknown by using Avogadro's number and you can go to grams of unknown if you know the molecular mass of the compound. Then, how do you go from moles of unknown to volume of unknown? Well, we just say simply, moles times molarity would give me liters.
Again, we're going to say, you use this chart when given a chemical reaction or chemical equation with a known quantity in either milliliters or liters or molarity of a compound or element and asked to find the unknown quantity of another compound or element.

This new Stoichiometric Chart is used anytime we are given the known quantity of a compound in units such as mL, L or M and asked to find the unknown quantity of another compound. 

Example: Molarity and Stoichiometry Calculation

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By using our new Stoichiometric Chart we can now answer stoichiometric questions dealing with molarity. 

Using our new Stoichiometric Chart it is possible to now calculate the unknown volume of a compound through molarity. 

Problem: How many milliliters of 0.325 M HCl are needed to react with 16.2 g of magnesium metal?

2 HCl (aq) + Mg (s) ----> MgCl2 (aq) + H2 (g)

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Knowing the volue and molarity of a compound allows us to determine the molarity of an unknown compound. 

Problem: What is the molarity of a hydrobromic acid solution if it takes 34.12 mL of HBr to completely neutralize 82.56 mL of 0.156 M Ca(OH)2?

2 HBr (aq) + Ca(OH)2 (aq) ----> CaBr2 (aq) + 2 H2O (l)

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Problem: Iron (III) can be oxidized by an acidic K2Cr2O7 solution according to the net ionic equation: Cr2O72- + 6 Fe2+ + 14 H+ -----> 2 Cr3+ + 6 Fe3+ + 7 H2O.  

If it takes 30.0 mL of 0.100 M K2Cr2O7 to titrate a 25 mL Fe2+ solution, what is the molar concentration of Fe2+?

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Solution Chemistry Additional Practice Problems

What volume of a 0.100 M HCl solution is required to exactly neutralize 25.0 mL of 0.235 M Ba(OH)2?

The balanced equation is 2HCl(aq) + Ba(OH)2 → BaCl2 + 2H2O(l).

a. 235 mL

b. 117.5 mL

c. 58.8 mL

d. 29.4 mL

e. 1.18 x 103 mL

Watch Solution

A 0.250 M solution of sulfuric acid (H2SO4) is to be reacted with a solution of sodium hydroxide via a double-displacement reaction to make sodium sulfate and water. 50.0 mL of the H2SO4 solution reacts with 25.0 mL of the NaOH solution. What is the molarity of the NaOH solution?

(A) 0.0625 M

(B) 0.125 M

(C) 0.250 M

(D) 0.500 M

(E) 1.00 M

Watch Solution

What mass of FeCl2 is needed to prepare 750.0 mL of 2.00 M solution?

(A) 47.6 g

(B) 95.3 g

(C) 127 g

(D) 190.5 g

(E) 190,500 g

Watch Solution

Lead(II) sulfide (PbS) was once used in glazing earthenware. It will also react with hydrogen peroxide (H2O2) to form lead(II) sulfate and water. How many grams of hydrogen peroxide are needed to react completely with 265 g of lead(II) sulfide?

(A) 151 g

(B) 123 g

(C) 37.7 g

(D) 9.41 g

(E) 265 g

Watch Solution

Barium hydroxide (used in corrosion inhibitors and lubricants) reacts with chloric acid (HClO3) to form barium chlorate [Ba(ClO3)2] and water. What mass of water is formed when 138 g of barium hydroxide reacts with chloric acid?

(A) 32.5 g

(B) 29.0 g

(C) 16.2 g

(D) 7.31 g

(E) 138 g

Watch Solution

How many moles of H3PO4 are produced when 36.5 g of HCl are produced by the reaction PCl5 + H2O → H3PO4 + HCl?

(A) 0.2 mol H3PO4

(B) 0.5 mol H3PO4

(C) 1 mol H3PO4

(D) 2 mol H3PO4

(E) 5 mol H3PO4

Watch Solution

A solution of hydrochloric acid is to be neutralized by using a 0.15 M solution of barium hydroxide. 25.0 mL of the HCl solution requires 33.3 mL of the Ba(OH)2 solution. What is the molarity of the HCl solution?

A. 0.40 M

B. 0.11 M

C. 0.15 M

D. 0.20 M

E. 0.22 M

Watch Solution

If a solution is supersaturated, then

A) the solute concentration is above the solubility limit, but the system is in equilibrium.

B) the solute concentration is below the solubility limit, and more solute can be dissolved.

C) the solute concentration is above the solubility limit, and the system is not in equilibrium.

D) the solute concentration is at the solubility limit.

E) no precipitate will form.

Watch Solution

The SO2 present in air is mainly responsible for the acid rain phenomenon. Its concentration can be determined by titrating against a standard permanganate solution as follows:

5 SO2 + 2 MnO4- + 2 H2O → 5 SO42- + 2 Mn2+ + 4 H+

Calculate the number of grams of SO 2 in a sample of air if 7.37 mL of 0.00800 M KMnO 4 solution are required for the titration.

Watch Solution

According to the following balanced reaction, how many moles of Fe(OH) 2 can form from 175.0 mL of 0.227 M LiOH solution?  Assume that there is excess FeCl2

            FeCl2(aq) + 2 LiOH(aq)  →  Fe(OH)2(s) + 2 LiCl(aq)

A) 3.97 × 10−2 moles

B) 2.52 × 10−2 moles

C) 1.99 × 10−2 moles

D) 5.03 × 10−2 moles

E) 6.49 × 10−2 moles

Watch Solution

When 5.0 grams of Na 2O (MM = 61.98 g/mol) are dissolved in 1.00 L of water, what is the concentration of the Na+ ions?

A.  0.040 M    

B.  0.080 M    

C.  0.16 M    

D.  6.2 M    

E.  12 M

Watch Solution

What is the molality of a solution made by dissolving 38 g of C 10H8 in 425 g of C7H8

a. 0.546 m

b. 12.3 m

c. 0.998 m

d. 4.65 m

e. 0.698 m 

Watch Solution

Use this chart when given a chemical equation with the  KNOWN quantity of a compound or element and asked to find the UNKNOWN quantity of another compound or element. 

Watch Solution

What is the molar mass of a 0.350 g sample of a monoprotic acid if it requires 50.0 mL of 0.440 M Ca(OH)2 to completely neutralize it? 

a) 5.30 g/mol

b) 7.95 g/mol

c) 31.8 g/mol

d) 47.7 g/mol

Watch Solution

Vinegar is a solution of acetic acid, CH 3COOH, dissolved in water. A 5.54 g sample of vinegar was neutralized by 30.10 mL of 0.100 M NaOH. What is the percent by weight of acetic acid in the vinegar?

a) 24.4 %

b) 0.109 %

c) 3.26 %

d) 9.79 %

Watch Solution

Blood alcohol (C2H5OH) level can be determined by titrating a sample of blood plasma with an acidic potassium dichromate, K2Cr2O7, solution. The balanced redox equation is given below:

H+ (aq) + 2 Cr2O72- (aq) + C2H5OH (aq) → 4 Cr3+ (aq) + 2 CO 2 (g) + 11 H2O (l)

If 45.12 mL of 0.04918 M Cr 2O72- solution is required to titrate 25.0 mL of C 2H5OH, what is the molar concentration of C2H5OH?

a. 0.05450 M

b. 0.01362 M

c. 0.17752 M

d. 0.04438 M

Watch Solution

Consider the following balanced redox equation: 

H2O  +  2 MnO4 +  3 SO32- →   2 MnO2  +  3 SO42-  +  2 OH

a)  How many moles of SO32- (MW:80.07 g/mol) are required to completely react with 20.3 mL of a 0.500 M MnO4 (MW: 118.90 g/mol) solution?

a. 0.0152 moles SO32-

b. 0.0067 moles SO32-

c. 0.005075 moles SO32-

d. 0.3045 moles SO32-

 

 

b) How many mL of a 1.25 M Na 2SO3 (MW: 126 g/mol) are required to completely react with 2.55 mL of a 3.50 M KMnO4 (MW: 158 g/mol) solution? 

 

 

 

 

 

c) How many grams of MnO 2 (MW: 86.94 g/mol) are produced when 32.0 mL of 0.615 M MnO 4- (MW: 118.90 g/mol) reacts with excess water and sulfite? 

 

Watch Solution

 How many moles of AgCl are formed from the reaction of 75.0 mL of a 0.078 M AgC2H3O2 solution with 55.0 mL of 0.109 M MgCl 2 solution?

2 AgC2H3O2 (aq) + MgCl 2 (aq) → 2 AgCl (s) + Mg(C2H3O2)2 (aq)

a. 0.0120 moles AgCl

b. 0.0117 moles AgCl

c. 0.00585 moles AgCl

d. 0.0600 moles AgCl

Watch Solution

How many moles of LiI are contained in 258.6 mL of 0.0296 M LiI solution?

A) 8.74 × 10-3 mol

B) 1.31 × 10-3 mol

C) 1.14 × 10-3 mol

D) 3.67 × 10-3 mol

E) 7.65 × 10-3 mol

Watch Solution

Which of the following does not affect the solubility of a solute in a given solvent?      

A) polarity of the solvent      

B) polarity of the solute

C) rate of stirring      

D) temperature of the solvent and solute

 

Watch Solution

When 5.0 grams of Na2O (MM = 61.98 g/mol) are dissolved in 1.00 L of water, what is the concentration of the Na + ions?

A. 0.040 M

B. 0.080 M

C. 0.16 M

D. 6.2 M

E. 12 M

Watch Solution

ln an acid-base titration, a 20.0 mL HCI solution of unknown concentration requires 15.6 mL of a 0.250 M NaOH solution to reach the equivalence point. What is the concentration (M) of the unknown HCI solution? 

HCl(aq) + NaOH(aq) → H2O(l) + NaCl(aq)

A. 12.1 M

B. 72.6 M

C. 320 M

D. 0.195 M

Watch Solution

What is the molarity of sodium ions in a solution prepared by diluting 250 mL of 0.550 M Na2SO4 to 1.25 L?

a) 0.110 M

b) 0.138 M

c) 0.220 M

d) 0.275 M

Watch Solution

Calculate the number of moles of iron(III)sulfide that forms when 62.0 mL of 0.135 M iron(III)chloride reacts with 45.0 mL of 0.285 M calcium sulfide.

a) 8.56 x 10−3 mol

b) 4.19 x 10−3 mol

c) 1.25 x 10−2 mol

d) 4.28 x 10−3 mol

e) 8.38 x 10−3 mol

Watch Solution

What volume of 0.131 M BaCl 2 is required to react completely with 42.0 mL of 0.453 M Na2SO4? The following is the net ionic equation.

Ba2+ (aq) + SO42- (aq) → BaSO4(s)

A. 12.1 mL

B. 72.6 mL

C. 145 mL

D. 290 mL

Watch Solution

What volume (L) of a 2.50 M SrCl 2 will completely react with 0.150 L of a 1.75 M AgNO3 solution?

SrCl2(aq) + 2AgNO3(aq) → 2AgCl(s) + Sr(NO3)2(aq)

A. 0.0525 L

B. 0.210 L

C. 0.0686 L

D. 0.429 L

Watch Solution

A chemistry student weighs out 0.0899 g of acetic acid, HC 2H3O2 into a 250 mL volumetric flask and dilutes to the mark with distilled water. He plans to titrate the acid with 0.1900 M NaOH solution. Calculate the volume of NaOH solution the student will need to add to reach the equivalence point.

a) 3.07 mL

b) 4.08 mL

c) 5.48 mL

d) 6.15 mL

e) 7.88 mL

Watch Solution

What is the molar mass of a 0.350 g sample of a monoprotic acid if it requires 50.0 mL of 0.440 M Ca(OH)2 to completely neutralize it? 

Watch Solution

Iron (III) can be oxidized by an acidic K2Cr2O7 solution according to the net ionic equation below. How many microliters of a 0.250 M FeCl2 are needed to completely react with 8.24 g of a compound containing 31.3% weight K2Cr2O7?

 

Cr2O7 2- + 6 Fe 2+ + 14 H+ → 2 Cr3+ + 6 Fe 3+ + 7 H2O

Watch Solution

In the following redox reaction, dichromate ion, Cr 2O7 2- , oxidizes Fe2+ to yield the following products.

Cr2O7 2- (aq) + 6 Fe 2+ (aq) + 14 H + (aq) → 2 Cr 3+ (aq) + 6 Fe 3+ (aq) + 7 H 2O (l)

If it takes 35.0 mL of 0.250 M FeCl 2 to titrate 100 mL of a solution containing Cr 2O7 2- , what is the molar concentration of Cr2O7 2-

a. 0.015 M

b. 0.053 M

c. 0.027 M

d. 0.045 M

Watch Solution

What volume of a 0.244 M KCl solution is required to react exactly with 50.0 mL of 0.210 M Pb(NO3)2 solution to the reaction below?

 

2 KCl (aq) + Pb(NO 3)2 (aq) → PbCl2 (s) + 2 KNO 3 (aq)

 

a. 97.4 mL

b. 116 mL

c. 43.0 mL

d. 86.1 mL

e. 58.1 mL

Watch Solution

What volume (in mL) of 0.500 M KMnO 4 is required to react with 0.2506 g of Cu+ according to the equation:

MnO4 + 5 Cu+ + 8 H+      ⇌       Mn2+ + 4H2

 

a) 1.58

b) 15.8

c) 7.9

d) 0.176

e) 0.100

Watch Solution

A 55.0 mL sample of a 0.102 M potassium sulfate solution is mixed with 35.0 mL of a 0.114 M lead (II) acetate solution and this precipitation reaction occurs:

K2SO4 (aq) + Pb(C2H3O2)2 (aq)      →       2 KC 2H3O2 (aq) + PbSO4 (s)

The solid PbSO4 is collected , dried, and found to have a mass of 1.01 g. Determine the limiting reactant, the theoretical yield, and the percent yield. 

Watch Solution

What volume of 0.305 M AgNO3 is required to react exactly with 155.0 mL of 0.274 M Na2SO4 solution? 

Watch Solution

The iron content in ores can be determined by titrating a sample with a solution of potassium permanganate. The ore is first dissolved in hydrochloric acid, forming iron (II) ions, which react with permanganate ions according to the following net-ionic reaction:

MnO4- (aq) + 5 Fe 2+ + 8H + (aq) → Mn 2+ (aq) + 5 Fe 3+ (aq) + 4 H 2O (l)

A sample of ore of mass 0.202g was dissolved in hydrochloric acid, and the resulting solution needed 16.7 mL of 0.0108 M KMnO4(aq) to reach the stoichiometric point.

What mass of iron (II) ions are present?

 

 

 

 

What is the mass percentage of iron in the sample of ore?

Watch Solution

Consider the following reaction sequence for the determination of dissolved oxygen in water:

 

2MnSO4(aq) + 4NaOH(aq) + O 2(aq) → 2MnO2(s) + 2Na2SO4(aq) + 2H2O(l)

MnO2(s) + 2H2SO4(aq) + 2NaI(aq) → MnSO 4(aq) + I 2(aq) + Na 2SO4(aq) + 2H 2O(l)

I2(aq) + 2Na 2S2O3(aq) → Na 2S4O6(aq) + 2NaI(aq)

 

If 9.00 mL of 0.0240 M Na 2S2O3(aq) are used in the analysis, how many moles of dissolved oxygen were determined?

a) 4.32 x 10-4 mol

b) 2.70 x 10-5 mol

c) 5.40 x 10-5 mol

d) 2.16 x 10-4 mol

e) 1.08 x 10-4 mol 

Watch Solution

Manganese in an ore can be determined by treating the ore with a measured, excess quantity of sodium oxalate (Na2C2O4) to reduce MnO2(s) to MnCl 2(aq) followed by determination of the unreacted sodium oxalate by titration with potassium permanganate. The equations for this two step process are:

 

MnO2(s) + Na2C2O4(aq) + 4HCl(aq) → 2MnCl 2(aq) + 2CO2(g) + 2H2O(l) +2NaCl(aq)

 

2KMnO4(aq) + 5Na2C2O4(aq) + 16HCl(aq) → 2MnCl 2(aq) + 10CO2(g) + 8H2O(l) + 10NaCl(aq)

 

If a sample is treated with 50.0 mL of 0.275 M Na 2C2O4(aq) and the unreacted Na 2C2O4(aq) requires 18.28 mL of 0.1232 M KMnO4(aq), calculate the number of grams of manganese in the sample. (NOTE: use the equations as written despite the fact they are not completely balanced) 

Watch Solution