CHEM FINAL (test2)

11) At 450C, 2.0 moles each of H2(g), I2(g), and HI(g) are combined in a 1.0 L rigid container. The value of Kc at 450C is 50. Which of the following will occur as the system moves toward equilibrium? a. More H2(g) and I2(g) will form. b. More HI(g) will form. c. The total pressure will decrease. d. No net reaction will occur, because the number of molecules is the same on both sides of the equation.

B

12) The reaction mixture represented below is at equilibrium at 298 K, and the molar concentrations are [X] = 1.0 M, [Y] = 5.0 M, [Z] = 5.0 M. What is the value of the equilibrium constant for the reaction at 298 K? X(g) + 2 Y(g) 3 Z (g) a. 1.0 b. 5.0 c. 25 d. 125

B

2 BaO2(s) 2 BaO(s) + O2(g) H = 162 kJ / molrxn 1) A sealed rigid vessel contains BaO2(s) in equilibrium with BaO(s) and O2(g) as represented by the equation above. Which of the following changes will increase the amount of BaO2(s) in the vessel? a. Adding a small amount of O2(g) b. Removing a small amount of BaO(s) c. Adding He gas to the vessel d. Increasing the temperature

B

6) A 1.0 mol sample of CO(g) and a 1.0 mol sample of H2(g) are pumped into a rigid, previously evacuated 2.0 L reaction vessel at 483 K. Which of the following is true at equilibrium? a. [H2] = 2 [CO] b. [H2] < [CO] c. [CO] = [CH3OH] < [H2] d. [CO] = [CH3OH] = [H2]

B

7) A mixture of CO(g) and H2(g) is pumped into a previously evacuated 2.0 L reaction vessel. The total pressure of the reaction system is 1.2 atm at equilibrium. What will be the total pressure of the system if the volume of the reaction vessel is reduced to 1.0 L at constant temperature? a. Less than 1.2 atm b. Greater than 1.2 atm but less than 2.4 atm c. 2.4 atm d. Greater than 2.4 atm

B

8) Based on the data above, what is the value for G for this reaction? a. G > 0 b. G < 0 c. G = 0 d. The value of G cannot be determined

B

CaCO3(s) CaO(s) + CO2(g) H = 178 kJ / molrxn 3) The reaction system represented above is at equilibrium. Which of the following will decrease the amount of CaO(s) in the system? a. Increasing the volume of the reaction vessel at constant temperature b. Lowering the temperature of the system c. Removing some CO2(g) at constant temperature d. Removing some CaCO3(s) at constant temperature

B

5) Which of the following explains the effect on the equilibrium constant, Kc, when the temperature of the reaction system is increased to 650 K? a. Kc will increase because the activation energy of the forward reaction increases more than that of the reverse reaction. b. Kc will increase because there are more reactant molecules than product molecules. c. Kc will decrease because the reaction is exothermic. d. Kc is constant and will not change.

C

2) At a certain point in time, a 1.00 L rigid reaction vessel contains 1.5 mol of PCl3(g), 1.0 mole of Cl2(g) and 2.5 mole of PCl5(g). Which of the following describes how the measured pressure in the reaction vessel will change and why it will change that way as the reaction system approaches equilibrium at constant temperature? a. The pressure will increase because Q < Kc. b. The pressure will increase because Q > Kc. c. The pressure will decrease because Q < Kc. d. The pressure will decrease because Q > Kc.

C

9) Which of the following statements is true about bond energies in this reaction? a. The energy absorbed as the bonds in the reactants are broken is greater than the energy released as the bonds in the product are formed. b. The energy released as the bonds in the reactants are broken is greater than the energy absorbed as the bonds in the product are formed. c. The energy absorbed as the bonds in the reactants are broken is less than the energy released as the bonds in the product are formed. d. The energy released as the bonds in the reactants are broken is less than the energy absorbed as the bonds in the product are formed.

C

10) At 25 C, the equilibrium constant (Kc) for the reaction represented above has a value of 1.3. At 50 C, the value of the equilibrium constant is less than 1.3. Based on the information, which of the following must be correct? a. The reaction is thermodynamically favorable only at temperatures above 25 C. b. At 25 C, G for the reaction is positive. c. At 25 C, S for the reaction is positive. d. At 25 C, H for the reaction is negative.

D

4) For which of the following reaction mixtures at equilibrium would reducing the volume of the container at constant temperature cause the equilibrium to shift toward the products? a. SrCO3(s) SrO(s) + CO2(g) b. C(s) + CO2(g) 2CO(g) c. PCl5(g) PCl3(g) + Cl2(g) d. 2NO2(g) N2O4(g)

D