Northrup's Chem 112 Section TTU General Chemistry

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Chem 112 - Quiz 5B - Spring, 1998 - Northrup

acid     Ka           pKa      Base            Kb           pKb
---------------------------------------------------------------------
HF     7.2 x 10-4     3.14     NH3          1.8 x 10-5     4.74
HNO2   4.5 x 10-4     3.35     methylamine  5.0 x 10-4     3.30
HAc    1.8 x 10-5     4.74
HOCl   3.5 x 10-8     7.45
HCN    4.0 x 10-10    9.4

1. What is the concentration of Cl- ions in an aqueous solution which is 0.20 M CaCl2?

a) zero
b) 0.20 M
c) 0.10 M
d) 0.40 M

2. Calculate the pH of 3.0 M NaOH(aq) solution.

a) -0.477
b) 14.47
c) 3.0
d) 11.0
e) 13.477

3. Calculate the hydroxide ion concentration in pure water at 25°C.

a) 1.0 x 10-7 M
b) 7.0 M
c) 1.0 x 10-14 M
d) exactly zero

4. Calculate the hydroxide concentration in 1.0 M HNO3(aq).

a) 1.0 x 10-7 M
b) 1.0 M
c) 1.0 x 10-14 M
d) 13.0 M

5. Calculate the pH of 1.0 M HBr(aq).

a) 7.0
b) 1.0
c) -1.0
d) 1.0 x 10-7
e) 0.0

6. What is the pH of 1.0 M NaCl(aq)?

a) 1.0
b) 7.0
c) 0.0
d) 1.0 x 10-7
e) 1.0 x 10-14

7. Calculate the H+ (aq) concentration of 0.50 M solution of HNO2.

a) 0.50 M
b) 0.015 M
c) 4.5 x 10-4 M
d) 0.30 M
e) 1.82 M

8. Calculate the percent ionization of the acid HF(aq) in 1.0 M aqueous HF solution.

a) 7.2 x 10-4 %
b) 0.072 %
c) 2.68 %
d) 100 %

9. Calculate the OH- concentration in 0.50 M aqueous NH3 solution.

a) 0.0030 M
b) 0.50 M
c) zero
d) 4.2 x 10-3 M

10. Calculate the pH of a 2.0 M aqueous solution of the base methylamine, which has a Kb = 5.0 x 10-4.

a) 2.0
b) 14.3
c) 13.3
d) 12.5
e) 3.3

11. An indicator symbolically given as HIn can be in two different forms: as HIn (red) or as In- (yellow). The pKa of the indicator is 4.0. What will be the color of the indicator in a solution which has a pH = 7?

a) red
b) yellow
c) a color intermediate between yellow and red

12. Calculate the pH of a solution which is formally 0.50 M HAc and 0.10 M NaAc.

a) -2.5
b) 4.74
c) 5.44
d) 2.52
e) 4.04

13. An aqueous solution of NH3 is in equilibrium. Suppose a gram of NH4Cl is added to the solution, and it is allowed to come to a new equilibrium. What will happen to the pH as a result of addition of NH4Cl?

a) It will go down.
b) It will go up.
c) It will remain unaffected.

14. Problem #13 is an example the common ion effect.

a) False
b) True

15. In Problem #13 the final solution is a buffer solution.

a) False
b) True

16. A solution is prepared which is 1.0 M HOCl and 1.0 M NaOCl. What is its pH?

a) 0.0
b) 3.72
c) 7.0
d) 7.45

17. A solution is prepared which is 1.0 M HCl and 1.0 M NaCl. What is its pH?

a) -1.0
b) 1.0
c) 0.0
d) 7.0
e) 4.74

18. A 1.00 Liter buffer solution is prepared which is 1.0 M in HAc and 1.0 M in NaAc. What would be the pH after 10.0 grams of NaOH were added to the solution?

a) 7.00
b) 4.74
c) 4.52
d) 5.74
e) 4.96

19. What is the H+(aq) concentration of 0.10 M NaAc(aq)?

a) 1.34 x 10-9 M
b) 7.45 x 10-6 M
c) 1.0 x 10-7 M
d) 1.34 x 10-3 M
e) 7.45 x 10-12 M

KEY

1)d 2)b 3)a 4)c 5)e 6)b 7)b 8)c 9)a 10)d 11)b 12)e 13)a 14)b 15)b 16)d 17)c 18)e 19)a
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