Problems A
367
PROBLEMS A
1. Calculate the ionization constants for each of the weak electrolytes in the
following table, using the experimental data given.
Electrolyte
(a) HCN
(b) HC 2 H 3 0 2
(c) NH 3
(d) HC 2 H 3 0 2
(e) HCHO 2
Concentration
1.00 M
0.00100 M
0.00690 M
0.200 M
0.200 M
[H
2.51 x
1.23 x
1.86 x
:*]
10^
5 M
10~
4 M
10~
3 M
103 M
IOH-]
3.38 x 10-" M
2. By pH meter or by color comparison with indicators, the solutions listed
below are found to have the pH values given. Calculate the ionization constant
for each.
(a) 0.0100 M HC 2 H 3 O 2 has a pH of 3.39
(b) 0.0500 M HCN has a pH of 5.25
(c) 0.0400 M NH 3 has a pH of 10.92
(d) 0.0200 M HCNO has a pH of 2.70
(e) 0.0100 M CH 3 NH 2 has a pH of 11.28
3. Calculate the pH of each of the following solutions.
(a) 0.500 M HCNO
(f) 1.50 M NH 3
(b) 0.100 M HN 3
(g) 0.500 M C 2 H 5 NH 2
(c) 0.0100 M H 3 BO 3
(h) 0.200 M C 5 H 5 N
(d) 0.250 M HC 2 H 3 O 2
(i) 0.00500 M NH 3
(e) 0.750 M HNO 2
(j) 1-25 M (CH 3 ) 3 N
4. Calculate the percentage of ionization of each of the following in water solution.
(a) 0.00300 M HCN
(d) 0.0500 M H 2 S
(b) 0.600 M HCHO 2
(e) 0.00100 M C 5 H 5 N
(c) 1.25 M (CH 3 ) 2 NH
5. A 5.00 g sample of HC 2 H 3 O 2 is added to 500 ml of water.
(a) What is the pH of the solution?
(b) Now 5.00 g of NaC 2 H 3 O 2 are added to the solution. What is the pH of the
solution now''
6. How many grams of NaC 2 H 3 O 2 must be added to 250 ml of a 0.100 M HC 2 H 3 O 2
solution to give a pH of 6.50?
7. A 10.0 ml sample of 2.00 M HC 2 H 3 O 2 is added to 30.0 ml of 1.00 M NaC 2 H 3 O 2 .
What is the pH of the solution?
8. A 5.00 g sample of NH 4 NO 3 is added to 100 ml of 0.100 M NH 3 . What is the pH
of the solution?
9. How many grams of NH 4 C1 must be added to 250 ml of 0.200 M NH 3 in order
that the solution shall have a pH of 7.20?