Ch. 15 & 16 equilibrium test [85 points] AP Chemistry

Show your work in an organized manner, includes any relevant equation / formula, proper units in your work / answer, and the proper number of significant figures in your answer.

1. Equilibrium constant. Justify your answer. [15 points]

a. If K_c = 100 for the reaction: N₂ + 3 H₂ <-->  2 NH₃,

then K_c = ___ for the reaction: 2 N₂ + 6 H₂  <-->   4 NH₃.

b. If K_c = 100 for the reaction:  3 Ca ²⁺_(aq)  + 2 PO₄ ^3-_(aq)  <-->  Ca₃(PO₄)_{2 (s)}

then K_c = ___ for the reaction:  Ca₃(PO₄)_{2 (s)}  <-->  3 Ca ²⁺_(aq)  + 2 PO₄ ^3-_(aq) 

c. If K_c = 100 for the reaction: 2 H_{2 (g)} + O _{2 (g)}   <-->   2 H₂O _(g)

then K_p = _____ for this reaction at 25 ° C.

2. At 400. K, does the reaction: 2 NH_{3 (g)}  -->   N_{2 (g)} + 3 H_{2 (g)} occur, where [NH₃] = 1.0 M, [N₂] = 1.0 mM, and [H₂] = 1.0 µ M ? Justify your answer. [15 points]

3. In the reaction: H₂ + I₂   <-->   2 HI    K_c = 10, determine the equilibrium concentration of HI, where the initial concentration of H₂, I₂, and HI are 1.0 M, 1.0 M, and 5.0 M, respectively. [15 points]

4. Determine the pH of a 125 mL aqueous solution containing 10.0 mM sodium lactate. [15 points]

5. In the reaction: C₂H_{4 (g)}   +   I_{2 (g)}  <-->   C₂H₃I _{3 (g)}   +    HI _(g) at equilibrium [C₂H₄ and C₂H₃I₃ is an alkene and alkane, respectively] , what would happen to [C₂H₃I₃] by the following disturbances. [justify your answer; 25 points]

a. remove I₂

b. reduce the system’s volume

c. cool the system [hint: sketch the structural formulas of the compounds in the reaction]