CHEMISTRY 162

PROBLEM REVIEW

SPRING 2009

  1. A reaction is 50% complete in 30.0 min. How long after its start will the reaction be 75% complete if it is
  2. First order
  3. Zero order
  1. The initial rate of the reaction A + B → C + D is determined for different initial conditions, with the results listed in the following table.

Experiment # / [A], M / [B], M / Initial Rate`
1 / 0.185 / 0.133 / 3.35x10-4
2 / 0.185 / 0.266 / 1.35X10-3
3 / 0.370 / 0.133 / 6.75X10-4
4 / 0.370 / 0.266 / 2.70X10-3
  1. What is the order of reaction with respect to A and to B?
  2. What is the overall reaction order?
  3. What is the value of the rate constant, K
  1. For the reaction A + 2 B → C + D, the following is 1.76x10-5 M/s at the time when [A]=0.3580 M.
  2. What is the rate of formation of C?
  3. What will [A] be 1.00 min later
  1. In the first-order reaction A→products, it is found that 99% of the original amount of reactant A decomposes in 137 min. What is the half-life, t1/2, of this decomposition reaction?
  1. The first-order reaction A→products has a half-life, t1/2 of 46.2 min at 25ºC and 2.6 min at 102ºC.
  2. Calculate the activation energy of this reaction.
  3. At what temperature would the half-life be 10.0 min?
  1. The reaction 2 NO + Cl2 → 2 NOCl has the rate law: R = k[NO]2[Cl2]. Propose a two-step mechanism for this reaction consisting of a fast reversible first step, followed by a slow step.
  1. Determine the Kp for the following equilibrium with the given Kc

N2O4 (g) ↔ 2NO2 (g)Kc = 2.9x10-2

  1. Given the fact that N2O4 (g) ↔ 2NO2 (g) has a Kc = 2.9x10-2

What would Kc be for the following equilibria

  1. 2N2O4 (g) ↔ 4NO2 (g)
  2. 1/2N2O4 (g) ↔ NO2 (g)
  3. 2NO2 (g)↔ N2O4 (g)
  1. A gaseous mixture containing 0.125 mole each of H2 (g) and I2 (g) is introduced into a 6.14 L flask at 445ºC, and equililibrium is established. What is the mole percent HI in the equilibrium mixture.

H2(g) + I2 (g) ↔ 2 HI (g) Kc=50.2

  1. What is the pH of each of the following solutions
  2. 0.045 M HClb. 0.045 M Ca(OH)2c. 0.104 M H2SO4
  1. Indicate whether each of the following is a Lewis acid or base.
  2. OH-b. (CH3)3Bc. CH3NH2
  1. A saturated aqueous solution of o-nitrophenol HOC6H4NO2, has pH=4.53. What is the solubility of o-nitrophenol in water, in grams per liter?

HOC6H4NO2 + HOH ↔ H3O+ + -OC6H4NO2 PKa = -7.23

  1. The H2PO4-/HPO42- combination plays a role in maintaining the pH of blood.
  2. Write equations to show how a solution containing these ions functions as a buffer.
  3. Verify that this buffer is most effective a pH 7.2
  4. Calculate the pH of a buffer solution in which [H2PO4-] = 0.050 M and [HPO4-]=0.150M
  1. If 100.0 mL of 0.0025 M Na2SO4 is saturated with CaSO4, how many grams of CaSO4 would be present in the solution.
  1. What is the minimum pH at which Cr(OH)3 will precipitate form a solution that is 0.086 M in Cr3+?
  1. Use the thermodynamic data in the appendix to determine the Ksp for AgBr
  1. A voltaic cell represented by the following cell diagram has Ecell = 1.250 V. What must be the [Ag+] in the cell?

Zn(s)׀Zn2+(1.00M)׀׀Ag+(xM)׀Ag(s)

  1. A voltaic cell is constructed as follows:

Ag(s)׀Ag+(sat Ag2CrO4)׀׀Ag+(0.125M)׀Ag(s)

What is the value of Ecell? For Ag2CrO4, Ksp=1.1x10-12