Name:  ________________                                                                                                            period:  _______

Ch. 16 & 17  equilibrium & acid / base / pH                  [65 points]                             Honors Chemistry

For problems involving calculations, show the relevant equation (or formula and conversion factor(s)), show your work in an organized manner, put the proper units in your calculations / answer, and have the proper number of significant figures in your answer. 

Academic Honesty:   The answers on this test are my own and I am using only the allowed set of notes as described in the syllabus.  I have not discussed the test questions with anyone before or during the test nor have I seen the test questions prior to the exam.  If you violate any of the preceding items or do not sign, your semester grade is a F.

                                                                                                Signature:  ___________________

1.  In the reaction:   2 C2 H6 (g)  +  7 O2 (g)    <->  4 CO2 (g)   +  3 H2 O(g) , the initial concentration of C2 H6 , O2 , CO2 ,  and H2 O are 2.0 M, 5.0 M, 0, and 0, respectively.  The equilibrium concentration of  O2 is 3.0 M.  What is the value of Kc ?   [10 points]

2.  What is the molar solubility of lead (II) chloride in water ?  [10 points]

3.  An exothermic reaction:  PCl3 (g)   +  Cl2 (g)   <->  PCl5 (g)   at equilibrium was disturbed by __; what is the effect on the concentration of Cl2 ?  Justify your response.  [15 points]

a.  increase the volume of the system

b.  remove PCl5 from the system

c.  heat the system

 

4.  fill-in the blank; show your work.  [10 points]

a.  if [H+ ] = 25 mM, then pH = __

b.  if pOH = 6.5, then [H+ ] = ___

 

5.   A buffer contains benzoic acid [C6 H5 COOH] and potassium benzoate [C6 H5 COOK].  Write the chemical equation describing the interaction between  __ and the buffer.   [10 points]

a.  hydrochloric acid

b.  potassium hydroxide

 

6.  What is the pH of 10.0 mM acetic acid (CH3 COOH) solution ?   [10 points]