Homework
Chapter 18




Homework 18.1

1. At equilibrium a mixture of N2, H2, and NH3 gas at 500oC is determined to consist of 0.602 mol/L of N2, 0.420 mol/L of H2, and 0.113 mol/L of NH3. What is the equilibrium constant for the reaction
N2(g) + 3 H2(g) = 2 NH3(g) at this temperature?
(0.286)

2. The reaction AB2C(g) = B2(g) + AC(g) reached equilibrium at 900 K in a 5.00 L vessel. At equilibrium 0.084 mol of AB2C, 0.035 mol of B2, and 0.059 mol of AC were detected. What is the equilibrium constant at this temperature for this system? ( 4.9 x 10-3)

3. At equilibrium a 1.0 L vessel contains 20.0 mol of H2, 18.0 mol of CO2, 12.0 mol of H2O, and 5.9 mol of CO at 427oC. What is the value of K at this temperature for the following reaction
CO2(g) + H2(g) = CO(g) + H2O(g)
(0.20)

4. A reaction between gaseous sulfur dioxide and oxygen gas to produce gaseous sulfur trioxide takes place at 600oC. At that temperature, the concentration of SO2 is found to be 1.50 mol/L, the concentration of O2 is 1.25 mol/L, and the concentration of SO3 is 3.50 mol/L. Calculate the equilibrium constant for the reaction
SO2(g) + 2 O2(g) = 2 SO3(g)
(4.36)

5. Write the chemical equilibrium expression for the reaction
4 HCl(g) + O2(g) = 2 Cl2(g) + 2 H2O(g)

6. For the reaction H2(g) + I2(g) = 2 HI(g) at 425oC, calculate [HI], given [H2] = [I2] = 4.79 x 10-4 mol/L and K = 54.3.
(3.53 x 10-3 mol/L)

Homework 18.2

1. Name three ways the chemical equilibrium can be disturbed.

2. Describe three situations in which ionic reactions go to completion.

3. Describe the common ion effect.

4. Identify the common ion in each of the following situations:
a) 5 g of NaCl is added to a 2.0 M solution of HCl;
b) 50 mL of 1.0 M NaCH3COO is added to 1.0 M CH3COOH;
c) 10 pellets of NaOH are added to 100 mL of water.

5. Predict the effect that decreasing pressure would have on each of the following reaction systems at equilibrium:
a) H2(g) + Cl2(g) = 2 HCl(g)
b) NH4Cl(s) = NH3(g) + HCl(g)
c) 2 H2O2(aq) = 2 H2O(l) + O2(g)
d) 3 O2(g) = 2 O3(g)

6. When solid carbon reacts with oxygen gas to form carbon dioxide, 393.51 kJ of heat are released. Does this reaction become more favorable or less favorable as the temperature decreases? Explain

Homework 18.3

1. What is meant by an acid ionization constant?

2. What is meant by the term buffered solution?

3. Which of the following combinations of solutions would form buffers when they are mixed?
a) 50 mL of 1.0 M HCl and 50 mL of 1.0 M NaCl;
b) 25 mL of 0.5 M HNO2 and 50 mL of 1.0 M NaNO2;
c) 25 mL of 1.0 M HNO2 and 25 mL of 1.0 M NaCl

4. a) What is meant by the ion product for water?
b) What is the value of this constant?

5. For each of the following reactions, identify each conjugate acid base pair:
a) H2CO3 + H2O = HCO3-1 + H3O+1

b) H2O + H2O = H3O+1 + OH-1

c) H2S + NH3 = HS-1 + NH4+1

d) H2PO4-1 + H2O = H3PO4 + OH-1

6. Which of the following ions hydrolyze in aqueous solution?
a) NO3-1

b) F-1

c) NH4+1

d) K+1

e) CH3COO-1

f) SO4-2

g) CO3-2

h) PO4-3

7. Identify the following solutions as acidic, basic or neutral:
a) 0.5 M KI;

b) 0.10 M Ba(OH)2

c) 0.25 M NH4NO3

d) 0.05 M BaCO3

8. Identify the acid and base from which each of the following salts was formed:
a) K2CrO4

b) Ca(CH3COO)2

c) CaF2

d) (NH4)2SO4

Homework 18.4

1. If the ion product exceeds the Ksp then
a) the solution is saturated; no more solid dissolves;
b) the solution is unsaturated; no more solid is present;
c) the solution is supersaturated and will readily precipitate

2. Silver carbonate, Ag2CO3, makes a saturated solution with Ksp = 1 x 10-11.
a) write the dissociation equation for the compound;
b) write the Ksp expression for the compound;
c) in the equilibrium system indicated by your equation in a), will the forward or reverse reaction be favored if extra Ag+1 is added; explain. soln

3. When the ionic, XCl2 dissolves in pure water to make a saturated solution, experiments show that 2 x 10-3 mol/L of X+2 ions go into solution.
a) write the dissociation equation for the compound;
b) write the expression for Ksp;
c) calculate the value for Ksp from the information given above. (3 x 10-8)

4. The solubility of Ag3PO4 is 2.1 x 10-4 g/100. g water.
a) write the dissociation equation for the compound;
b) calculate the concentration of each ion in solution; (5 x 10-6 M)
c) calculate the value for Ksp for the compound. ( 1.7 x 10-20 )


Homework 18.5

1. What is the value of Ksp for Ag2SO4, if its solubility is 5.40 g /100 g water. (2.07 x 10-5) soln

2. Determine if a precipitate will form if 20 mL of a 1.00 x 10-7 M AgNO3 solution is mixed with 20 mL of a 2.00 x 10-9 M NaCl solution at 25 degrees Celsius. (No, Why?) soln

3. A solution of AgI contains 2.7 x 10-10 mol/L silver ions. What is the maximum amount of iodide ion concentration that can exist in this solution? (3.1 x 10-7 mol/L)

4. Calculate whether a precipitate will form is 0.35 L of 0.0044 M Ca(NO3)2 and 0.17 L of 0.00039 M NaOH are mixed at 25 degrees Celsius. See table 18-3 for Ksp values. (No)