Arkansas State University  Department of Chemistry and Physics
CHEM1023	Exam 4

1.  Calculate the pH of a hydroiodic acid solution with a [H⁺] = 2.3 x 10^-2 M.   (4 points)

2.  Calculate the pH of a 0.0002 M KOH solution.   (6 points)

3.  Write the equilibrium equation and calculate the equilibrium concentrations of a 0.5 M HCN solution.  K_a = 4.0 x 10^-10    (10 points)

4.  Write the equilibrium equation and calculate the pH of a 0.6 M pyridine solution.  (10 points)  K_b = 2.0 x 10^-9  (Formula for pyridine is C₅H₅N)

5. Calculate the K_a for a 0.3 M HF solution with a pH of 1.84.  (10 points)

6.  Circle the combinations which could serve as buffer solutions.        (10 points)
 

a)  HCl / NaCl	b) NH3 / (NH4)2SO4
c) H2O / NaOH	d)  HOCl / KOCl
e) H3PO4/ KH2PO4

7. Calculate the pH of a buffer solution made from 0.40 M acetic acid and 0.60 M sodium acetate.  K_a = 1.8 x 10^-5   (10 points)

8. Calculate the pH of a buffer solution made from 0.60 M acetic acid and 0.60 M sodium acetate after the addition of 0.08 mol of NaOH.  Assume no change in volume. K_a = 1.8 x 10^-5  (10 points)

9.  What would be the buffer range for an acid if its K_a = 1.6 x 10^-5 ?    (6 points)

10.  For each of the following, define the resulting solutions as either acidic, basic or neutral.  (2 points each)

a) NaOOCCH₃

b)  NO₂

c)  CaO

d)  ammonium bromide

e)  KCl

11.  Draw a titration curve that would represent a titration of a strong acid with a weak base.  Label all parts and indicate the expected pH for the equivalence point.   (10 points)

12. Define an amphoteric oxide.  (4 points)