Problems B
369
20. Compute the pH for each of the points shown in Figure 23-1. The titration
involves the successive addition of 0.00, 5.0, 10.0, 24.0, 24.9, 25.0, 25.1, 26.0,
and 30.0 ml of 0.100 M NaOH to 25.0 ml of 0.100 M HC 2 H 3 O 2 .
21. Compute pH values and construct a curve for the titration of HC1 by NaOH.
Assume that an initial volume of 25.0 ml of 0.100 M HC1 is used and is titrated
by 0.100 M NaOH. Make calculations for additions of 0.00, 5.0, 10.0, 24.0,
24.9, 25.0, 25.1, 26.0, and 30.0 ml of NaOH solution.
PROBLEMS B
22. Experimental measurement shows that each of the following is ionized in
water as shown. Calculate the ionization constant for each.
(a) 0.100 M HF is 7.89% ionized
(b) 0.200 M HNO 2 is 4.94% ionized
(c) 0.100 M HC 2 H 3 O 2 is 1.31% ionized
(d) 0.250 M NH 3 is 0.83% ionized
(e) 0.200 M HAsO 2 is 0.0055% ionized
23. 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 HNO 2 has a pH of 2.69
(b) 0.00100 M HN 3 has a pH of 3.89
(c) 0.00500 M HCN has a pH of 5.75
(d) 0.200 M (CH 3 ) 2 NH has a pH of 12.02
(e) 0.00200 M C 6 H 5 NH 2 has a pH of 7.96
24. Calculate the pH of each of the following solutions.
(a) 0.00200 M HCN
(f) 2.50 M CH 3 NH 2
(b) 0.750 M HCHO 2
(g) 0.500 M NH 3
(c) 1.20 M HF
(h) 1.75 M C 6 H 5 NH 2
(d) 0.00200 M H 3 BO 3
(i) 0.75 M (CH 3 ) 2 NH
(e)0.100MH 2 S
(j) 0.0200 M NH 3
25. Calculate the percentage of ionization of each of the following in water solution.
(a) 0.00500 M C 5 H 5 N
(d) 1.25 M NH 3
(b) 0.800 M HN 3
(e) 2.50 M HF
(c) 0.650 M HCNO
26. A 10.0 g sample of formic acid is added to 200 ml of water.
(a) What is the pH of the solution?
(b) Now 20.0 g of sodium formate are added to the solution. What is the pH of
the resulting solution?
27. How many grams of NaNO 2 must be added to 300 ml of a 0.200 M HNO 2
solution to give a pH of 4.70?