Ch.  16 & 17  acid / base /  pH & equilibrium                test                          70 points                                                               chemistry
Show your work in an organized manner, include (i) any relevant equation (or formula), (ii) conversion factor(s), (iii) put the proper units in your calculations and answer, and (iv) have the proper number of significant figures in your answer. 

1. Write the algebraic expression for the equilibrium constant for the following reactions.  [10 points]

a. Ca2+(aq)  +  PO43-(aq)  ⇔  Ca3(PO4)2(s)

b. CH3COOH(aq)  +  H2O(l) ⇔  H3O+(aq)  +  CH3COO-(aq)

2. What is the numerical value of the equilibrium constant for the reaction:  N2(g)  +  3 H2(g)  F  2 NH3(g)  if the initial [N2] and [H2] are 5.0 M and 8.0 M, respectively, and the equilibrium [H2] is 5.0 M.  [10 points]

3. What is the pH of __  ?  [10 points]

a. 25 mM nitric acid, a strong acid

b. 25 mM potassium hydroxide, a strong base.

4. What is the pH of a 25 mM benzoic acid, C6H5COOH, a weak acid ?  The Ka of this acid is 6.5 * 10 -5.  [10 points]


5. In the reaction:  H2(g)  +  F2(g)  ⇔  2 HF(g), the value of Kc = 10.0 and the initial [H2] and [F2] are 3.0 M and 4.0 M, respectively.  What is the equilibrium [HF] ?  [10 points]


6. In regards to the reaction:  PCl3(g)  +  Cl2(g)  ⇔  PCl5(g) at equilibrium is disturbed by  __; what is the effect on the number of moles of PCl5 ?  Justify / rationalize your response.  [20 points]

a. What is the algebraic expression for the reaction quotient of the preceding reaction ?  

b. addition of neon only, an inert gas

c. removal of  Cl2 only

d.  increase the volume