Write the Equilibrium Expression, Kc for the Following Reaction

Write the Equilibrium Expression, Kc for the Following Reaction

Chapter 15 Exam Review 2
Supplemental Instruction
Iowa State University / Leader: / Yee
Course: / CHEM 178
Instructor: / Dr. Irmi
Date: / 10/17/2015

Warm up:

Write the equilibrium expression, Kc for the following reaction:

Ag+ (aq) + 2 NH3 (aq) Ag(NH3)2+

Multiple choice questions:

1) At 300°C, Kp is 4.34 × 10–3 for the reaction N2 (g) + 3 H2 (g) 2 NH3 (g). What is Kc at this temperature?

(a) 9.60(b) 2.98 x 10-2 (c) 204.07(d) 9595

2) For the reaction N2O4 (g) 2 NO2 (g) at 100°C, NO2 is favored. Which of the following is true?

(a) K = 1(b) K = 0(c) K > 1(d) K < 1

3) For the reaction H2 (g) + I2 (g) 2 HI (g), Kp = 794 at 298 K and Kp = 55 at 700 K. Which of the following is true?

(a) The formation of HI is favored more at higher temperature

(b) The formation of HI is favored more at lower temperature

(c) The formation of HI is the same regardless of temperature

(d) The formation of H2 and I2 are favored more at both temperatures.

4) Consider the equilibrium H2O (g) + CO (g) H2 (g) + CO2 (g) at 1000K, Kc = 0.838. The initial concentrations at 1000 K are set so that Qc = 0.389. Which of the following is true?

(a) Equilibrium cannot be re-established

(b) The system is at equilibrium

(c) A reaction occurs to form H2O (g) + CO (g)

(d) A reaction occurs to form H2 (g) + CO2

Short answer questions:

Question 1-3 refer to the equilibrium reaction:

HF (aq) H+ (aq) + F- (aq)Kc = 6.8 x 10-4

1) Calculate equilibrium constant (Kc) for the reaction ½ HF (aq) ½ H+ (aq) + ½ F- (aq).

2) Calculate equilibrium constant (Kc) for the reaction 2H+ (aq) + 2F- (aq) 2HF (aq).

3) Given that Kc for the reaction H2C2O4 (aq) 2 H+ (aq) + C2O42- (aq) is 3.8 x 10-6. Calculate equilibrium constant (Kc) for the reaction

2 HF(aq) + C2O42- (aq) 2 F- (aq) + H2C2O4.

Question 4-6 refer to the equilibrium reaction:

N2O4 (g) 2 NO2 (g)

4) Predict the direction of the reaction when the concentration of NO2 increases.

5) Consider the equilibrium is achieved in a closed container. If the pressure in the container is increased, which direction will the reaction proceed?

6) It has been determined that the reaction above is endothermic. If the temperature of the system is increased, which direction will the reaction proceed?

7) Sulfur trioxide decomposes at high temperature in a sealed container: 2 SO3 (g) 2 SO2 (g) + O2 (g). Initially, the vessel is charged at 1000K with SO3(g) at a partial pressure of 0.500 atm. At equilibrium the SO3 partial pressure is 0.200 atm. Calculate the value of Kp at 1000K.

Chapter 16 Exam Review 2
Supplemental Instruction
Iowa State University / Leader: / Yee
Course: / CHEM 178
Instructor: / Dr. Irmi
Date: / 10/17/2015

Multiple choice questions:

1) In basic aqueous solutions, which of the following is always true?

(a) [H+] > 10-7 (c) [H+] > [OH-]

(b) [OH-] > 10-7 (d) [OH-] > [H+]

2) Which one of the following 0.10 M solutions has the highest pH value at 25°C?

(a) NaNO2(aq) (b) NaHSO3(aq) (c) NaI(aq) (d) NaClO4(aq)

3) For the following equilibrium

CN (aq) + HNO2 (aq) HCN (aq) + NO2 (aq),K = 9.2 × 105

Which species is the strongest Brønsted-Lowry acid?

(a) CN (aq) (b) HNO2 (aq) (c) HCN (aq) (d) NO2 (aq)

4) What is the value of the equilibrium constant for the following equilibrium?

HCN(aq) + OH- (aq) CN (aq) + H2O(l)

(a) Ka(HCN) (b) 1 / Ka(HCN) (c) Kb(CN– ) (d) 1 / Kb(CN– )

5) In tryptophan, the Ka for the carboxylic acid group is 4 × 10–3 and Kb for the amine is 2 × 10–5 . When tryptophan is dissolved in water, it forms ______solution.

(a) a basic(b) an acidic(c) a neutral(d) none of the above

Short answer question:

1) For each of the following pairs, write the stronger base and its conjugate acid.

Stronger Base / Its Conjugate Acid
NO3 (aq) or NO2(aq)

ClO4 (aq) or ClO2 (aq)

2) Estimate the pH of the 0.30 M NaClO(aq) solution. ( Kb(ClO) = 5.0  106 ).

3) Calculate the pH of a solution of 10-8 M NaOH.

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