Ch. 17 & 20  equilibrium II & electrochem      test                 [115 points]                             AP Chem

 

For problems involving calculations, show your work in an organized manner, include any relevant equation (or formula and conversion factor(s)), put the proper units in your calculations / answer, and have the proper number of significant figures in your answer.  Clearly identify the problems done and do them in sequence and your answer must begin and end on the same page of paper; otherwise, you will lose points.  attach this sheet to the front of your exam.

 

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.  What is the solubility of Co(OH)2 in  __.  [20 points]

 

a.  water

 

b. buffer @ pH = 9.60

 

2.  A 50.0 mM aqueous solution of sodium carbonate was slowly added to a 75.0 mL aqueous solution containing 1.0 mM Cu2+ , 1.0 mM Ba2+, and 1.0 mM Ca2+  –  identify the first precipitate to form – justify your response.  [15 points]

 

3.  100.0 mL buffer contains 10.0 mM acetic acid and 20.0 mM sodium acetate.  [20 points]

 

a.  5.0 mL 10.0 mM hydrochloric acid was added to the buffer.  What is the pH of the buffer after the addition of the hydrochloric acid. ?

 

b.  5.0 mL 10.0 mM potassium hydroxide was added to the buffer.  What is the pH of the buffer after the addition of the potassium hydroxide ?

 

4.  balanced the redox reaction (in an acidic solution):    [10 points]

 

5.  In regards to the hydrolysis of water,  [15 points]

 

a.  sketch the electrolytic cell

 

b. label the cathode / anode & write half-reaction at the appropriate electrode

 

c.  show the direction of the current

 

6.  In an electroplating experiment to coat an electrode with zinc, you have 15.0 minutes to coat 100.0 mg Zn onto the electrode.  What is the current ?  [10 points]

 

7.  In the redox reaction: ; what is the cell potential @ 25 °C ?  [15 points; sample problem 20.11]

 

8.  old topic:  what is the trend in acid strength in a __ in the periodic table;  what is the rationale of this trend ?  [10 points] 

 

a.  row

 

b.  column