Problem 85
\(100 \mathrm{~mL}\) of \(0.02 \mathrm{M}\) benzoic acid \(\left(p K_{a}=4.20\right.\) ) is titrated utsing \(0.02 \mathrm{M} \mathrm{NaOH}, \mathrm{pH}\) after \(50 \mathrm{~mL}\) and \(100 \mathrm{~mL}\) of \(\mathrm{NaOH}\) have been added are: (a) \(3.50,7\) (b) \(4.2,7\) (c) \(4.2,8.1\) (d) \(4.2,8.25\)
Problem 86
What is the \(\mathrm{pH}\) of a solution of \(0.28 \mathrm{M}\) acid and \(0.84 \mathrm{M}\) of its conjugate base if the ionization constant of acid is \(4 \times 10^{-4}\) ? (a) \(3.88\) (b) \(3.34\) (c) 7 (d) \(10.12\)
Problem 87
The toxic compound 2,4-dinitrophenol has \(K_{a}=10^{-4} M\). In an experiment, a buffer solution of 2,4 -dinitrophenol was prepared with the \(\mathrm{pH}\) adjusted to \(5 .\) Calculate the ratio of the concentrations of the dissociated ion to the undissociated acid : (a) \(0.01\) (b) \(0.1\) (c) 10 (d) 100
Problem 90
The acid dissociation constant of uric acid is \(K_{a}=4.0 \times 10^{-6} M\). The \(\mathrm{pH}\) of a sample is \(6.0\). What is the ratio of urate ion to uric acid in the urine? (a) \(2.0\) (b) \(4.0\) (c) \(6.0\) (d) \(0.25\)
Problem 91
\(\mathrm{CH}_{3} \mathrm{NH}_{2}\) (1.2 mole, \(\mathrm{pK}_{b}=3.3\) ) is added to \(0.08\) moles of \(\mathrm{HCl}\) and the solution is diluted to one litre, resulting \(\mathrm{pH}\) of solution is : (a) \(10.7\) (b) \(3.6\) (c) \(10.4\) (d) \(11.3\)
Problem 92
An aqueous solution at room temperature is \(0.1 M\) with respect to ammonium chloride and \(0.01 M\) with respect to \(\mathrm{NH}_{4} \mathrm{OH}\left(\mathrm{pK}_{b}=5\right)\), the \(\mathrm{pH}\) of the solution is : (a) 75 (b) \(6.8\) (c) \(6.5\) (d) \(8.0\)
Problem 93
Which of the following will decrease with dilution at a given temperature? (a) \(\mathrm{pH}\) of \(10^{-3} \mathrm{M}\) acetic acid solution (b) \(\mathrm{pH}\) of \(10^{-3} \mathrm{M}\) aniline solution (c) degree of dissociation of \(10^{-3} \mathrm{M}\) acetic acid (d) degree of dissociation of \(10^{-3} \mathrm{M}\) aniline solution
Problem 94
A \(1 L\) solution contains \(0.2 \mathrm{M} \mathrm{NH}_{4} \mathrm{OH}\) and \(0.2 \mathrm{M} \mathrm{NH}_{4} \mathrm{Cl}\). If \(1.0 \mathrm{~mL}\) of \(0.001 \mathrm{M} \mathrm{HCl}\) is added to it. What will be the \(\left[\mathrm{OH}^{-}\right]\) of the resulting solution \(\left(K_{b}=2 \times 10^{-5}\right)\) (a) \(2 \times 10^{-5}\) (b) \(5 \times 10^{-10}\) (c) \(2 \times 10^{-3}\) (d) None of these
Problem 98
The \(\mathrm{pH}\) of a solution of \(0.10 \mathrm{M} \mathrm{CH}_{3} \mathrm{COOH}\) increases when which of the following substances is added? (a) \(\mathrm{NaHSO}_{4}\) (b) \(\mathrm{HClO}_{4}\) (c) \(\mathrm{KNO}_{3}\) (d) \(\mathrm{K}_{2} \mathrm{CO}_{3}\)
Problem 100
\(\mathrm{pK}_{a}\) of \(\mathrm{NH}_{4}^{+}\) is \(9.26 .\) Hence, effective range for \(\mathrm{NH}_{4} \mathrm{OH}-\mathrm{NH}_{4} \mathrm{Cl}\) buffer is abouts (a) \(8.26\) to \(10.26\) (b) \(4.74\) to \(5.74\) (c) \(3.74\) to \(5.74\) (d) \(8.26\) to \(9.26\)
