Engineering Chemistry S Datta

IONIC EQUILIBRIUM 203
21. What will be the pH of a solution obtained by mixing 800 ml of 0.05 (N) NaOH and 200 ml of 1N
HCl? [Ans. 12.3]
22. Calculate the pH and pOH of .1N HCl. [Ans. 1, 13]
23. Find α for NH 4
OH in a solution of .1M. Given K b
= 2 × 10 –5 . [Ans. .014]
24. What will be the pH of a solution obtained by mixing 5g. of CH 3
COOH and 7.5 g. of CH 3
COONa,
making a volume equal to 500 ml? [Ans. 4.78]
25. pH of a solution is 10.57. Calculate the [H + ]. [Ans. 2.69 × 10 –11 moles l –1 ]
26. Calculate the pH and pOH of:
(a) 0.00345 (N) acid (b) 0.000775 (N) acid
(c) 0.00886 (N) base [Ans. (a) 2.46, 11.54 (b) 3.11, 10.89 (c) 11.95, 2.05]
assuming complete dissociation.
27. Solubility of PbSO 4
is 0.038 g-l –1 . Calculate its solubility product. [Ans. 1.6 × 10 –8 ]
28. Solubility of Ag 2
CrO 9
g-l –1 . Calculate its solubility product. [Ans. 1.4 × 10 –12 }
29. [Ag + ] in a solution is 4 × 10 –3 g-in l –1 . Calculate the minimum concentration of Cl – to precipitate
AgCl. Given K sp
of AgCl = 1.8 × 10 –10 . [Ans. 5 × 10 –8 g-in l –1 ]
30. Calculate the concentration of H 2
S required to arrest the precipitation of PbS from a solution of
0.001 (M) Pb(NO 3
) 2
. Given K a
(H 2
S) = 1.1 × 10 –23 , K sp
(PbS) = 3.4 × 10 –28 . [Ans. 5.6 (M)]