SI Exam I Review
Supplemental Instruction
Iowa State University / Leader: / Ryan Gale
Course: / Chem 178
Instructor: / Burnett/Raker
Date: / 2/10/13

1.)Which statement is true:

  1. The formation of solutions is favored by an increase in entropy.
  2. The formation of solutions is favored by a decrease in entropy.
  3. The formation of solutions is favored by an increase in enthalpy.
  4. The formation of solutions is favored by a decrease in enthalpy.

2.)The mole fraction of a particular insoluble compound in water is 0.1 at 25 °C. The vapor pressure of pure water at this temperature is 760 torr. What is the change in pressure over the solution?

  1. -7.6 torr
  2. 1 atm
  3. -76 mmHg
  4. 100 kPa

3.)A commercial bleaching solution contains 3.62 mass % sodium hypochlorite, NaOCl. What is the mass of NaOCl, in grams, in a bottle containing 2.50 kg of bleaching solution?

  1. 9.05 g
  2. 90.5 kg
  3. 90.5 g
  4. 9050 g

4.)A solution containing equal masses of glycerol, C3H8O3 and water has a density of 1.10 g/mL. Calculate the molality and molarity of glycerol in solution.

  1. 0.00598 M C3H8O3, 10.87 m C3H8O3
  2. 5.98 M C3H8O3, 10.87 m C3H8O3
  3. 5.98 M C3H8O3, 0.01087 m C3H8O3
  4. 10.87 M C3H8O3, 5.98 m C3H8O3

5.)List the following aqueous solutions in order of increasing boiling point: 0.120 m glucose, 0.050 m LiBr, 0.050 m Zn(NO3)2.

  1. Glucose, Zn(NO3)2, LiBr
  2. Zn(NO3)2, LiBr, glucose
  3. LiBr, glucose, Zn(NO3)2
  4. Glucose, LiBr, Zn(NO3)2

6.)What is the freezing point of an aqueous solution that boils at 105.0 °C. For aqueous solutions, Kb = 0.51 °C/m and Kf = 1.86 °C/m.

  1. 0 °C
  2. 1.37 °C
  3. -1.37 °C
  4. -18.2 °C

7.)Indicate whether the following statements are true or false:

  1. At equilibrium, the concentrations of reactants and products are constant.
  2. The equilibrium constant does not depend on the reaction stoichiometry.
  3. Kc in one direction is the inverse of the constant in the backwards direction.
  4. It is not possible to know how a reaction will shift unless it is at equilibrium.

8.)Which of the following statements are correct for the following equilibrium (check all that apply): 1/2N2(g) + 1/2O2(g) ↔ NO(g) ΔH° = 90.4 kJ

  1. The equilibrium will not shift by changing the system pressure.
  2. The reaction will shift left as the temperature of the vessel increases.
  3. The reaction is undergoing a homogeneous equilibrium.
  4. Venting the partial pressure of nitrogen increases the oxygen partial pressure.

9.)Consider the equilibrium:

CoO(s) + H2(g) ↔ Co(s) + H2O(g)Kc = 67

CoO(s) + CO(g) ↔ Co(s) + CO2(g)Kc = 490

What will Kc be for the reaction:H2(g) + CO2(g) ↔ CO(g) + H2O(g)

  1. 33000
  2. 7.3
  3. 0.14
  4. 3.0*10-5

10.)The stronger a ______, the weaker its ______, and the stronger the

______, the weaker its ______.

11.)What is the concentration of a solution of KOH for which the pH is 11.89?

  1. 7.8*10-3M
  2. 2.4 * 10-3M
  3. 12.9 * 10-2 M
  4. 1.29 * 10-26 M

12.)What is the conjugate of HCOOH?

  1. COOH-
  2. HCOOHH+
  3. HCOO-
  4. COO2-

13.)What is the pH of a 0.040 M solution of HClO4?

  1. -1.40
  2. 1.40
  3. -1.10
  4. 1.10

14.)At 27 °C, N2(g) + 3H2(g) ↔ 2NH3(g)Kp = 4.34 * 10-3

If 2.5 atm N2 and 6 atm of NH3 exist at equilibrium, how much H2 is present?

  1. 0.0670 atm
  2. 14.9 atm
  3. 2.74 atm
  4. 3.65 atm

15.)Acetonitrile (CH3CN) is a polar organic solvent that dissolves a wide range of solutes, including many salts. The density of a 1.80 M LiBr solution in acetonitrile is 0.826 g/cm3. Calculate the following concentrations:

  1. The molality of the solution
  1. The mole fraction of LiBr
  1. The mass percentage of CH3CN

16.)At 218 °C, Kc = 1.2 * 10-4 for the equilibrium

NH4SH(s) ↔ NH3(g) + H2S(g)

Calculate the equilibrium concentrations of NH3 and H2S if a sample of solid NH4SH is placed in a closed vessel at 218 °C and decomposes until equilibrium is reached.

17.)The equilibrium constant Kc for the reaction:

C(s) + CO2(g) ↔ 2 CO(g)Kc = 1.9 at 1000 K, and 0.133 at 298 K.

If excess C is allowed to react with 25.0 g of CO2 in a 3.00 L vessel at 1000 K, how many grams of CO are produced? Is the reaction endothermic or exothermic?

18.)An equilibrium mixture of H2, I2 and HI at 458 °C contains 0.112 mol H2, 0.112 mol I2, and 0.775 mol HI in a 5.00 L vessel. What are the equilibrium partial pressures when equilibrium is reestablished following the addition of 0.200 mol of HI?

19.)Complete the following table, you can show your work below the table:

Problem / [H+] / [OH-] / pH / pOH / Acidic/basic
a.) / 7.5 * 10-3 M
b.) / 5.70

20.)Lactic acid (CH3CH(OH)COOH) has one acidic hydrogen. A 0.10 M solution of lactic acid has a pH of 2.44. Calculate Ka.

Formulas:

ΔTf = Kf • m

ΔTb = Kb • m

PA = XAPA

PT = PA + PB

R = 0.0821 L atm/K mol = 8.314 J/mol K

T (K) = °C + 273.15

Kw = 1.0 × 10-14at 298 K

Kw = Ka × Kb

pH = -log[H3O+]

pOH = -log[OH-]

pH + pOH = 14.00