Ps1

Chemical Equilibrium

Problem Set # 1

MMXv.1

Instructions: Write your answer in one whole sheet of paper using black/blue pen. Show solution when necessary. Erasures should be made using correction tape/fluid. Write legibly. A.

Balance and give the equilibrium constant expression for the following chemical reactions: 2+ 1. H2CO3 (aq) + H2O (l)  CO3 (aq) + H3O (aq) KC + + 2. Ag (aq) + NH3 (aq)  Ag(NH3)2 (aq) KC + 2+ 3. H (aq) + Cu (s)  H2 (g) + Cu (aq) KC/P 4. POCl3 (g)  PCl3 (g) + O2 (g) KC/P 5. SO3 (g) + H2SO4 (l)  H2S2O7 (l) KC/P

B.

Compare the KP and KC of part A, 3-5 (<, >, =) 3. KC ____ KP 4. KC ____ KP 5. KC ____ KP

C.

At 448oC, the KP for the reaction H2(g) + I2(g)  2HI(g) is 51. Predict in which direction the reaction will proceed to reach equilibrium if 0.020 mole of hydrogen iodide, 0.010 mole of hydrogen gas, and 0.030 mole of iodine gas were placed in a 2.0-liter flask. Show your solution.

D.

Using the same reaction in part C, graph the partial pressure versus time as it approaches equilibrium when additional hydrogen gas is added to a system initially in equilibrium.

E. Is it possible to have a negative reaction quotient? Explain your answer. F.

At 298 Kelvin, Kc = 1.6 x 10 – 2 for 2H2S(g)  2H2(g) + S2(g) , Calculate KP for 5H2S(g)  5H2(g) + 2.5S2(g) Show your solution.

G. Oxalic acid can donate two protons to water in successive reactions: + 1) H2C2O4 (aq) + H2O(l) H3O (aq) + HC2O4 (aq) + 2– 2) HC2O4 (aq) + H2O(l) H3O (aq) + C2O4 (aq) If Kc1 = 5.9x10–2 and Kc2 = 6.4x10–5 at 25°C, what is the value of KC for reaction (3)? Show your solution. 3) H2C2O4 (aq) + 2 H2O(l)  2 H3O+(aq) + C2O42–(aq)