Problem 94
\(A\) mixturc of a weak acid (say acctic acid) and its salts with a strong basc (say sodium acetate) acts as a buffcr solution. Which other pair has similar properties? (1) IICl and \(\mathrm{NaCl}\) (2) \(\mathrm{NaOII}\) and \(\mathrm{NaNO}_{3}\) (3) KOII and KCl (4) \(\mathrm{NII}_{4} \mathrm{OII}\) and \(\mathrm{NII}_{4} \mathrm{Cl}\)
Problem 95
In a chemical reaction reactants \(\rightleftharpoons\) products is shifted towards the products both by increase of pressure and rise in temperature then the forward reaction is (1) endothermic with \(\Delta n\) positive (2) exothermic with \(\Delta n\) positive (3) exothermic with \(\Delta n\) negative (4) endothermic with \(\Delta n\) negative
Problem 96
In a buffer solution consisting of a weak acid and its salt, the ratio of concentration of salt to acid is increased 10 fold, then the \(\mathrm{pH}\) of the solution will (1) increase by one (2) increase by 10 fold (3) decrease by one (4) decrease by 10 fold
Problem 97
Which of the following statements is wrong? (1) for an acid buffer solution the \(\mathrm{pH}\) can be increased by inereasing the concentration of salt (2) for a basic buffer solution the pH can increased by decreasing the concentration of base(3) buffer capacity of a buffer solution is maximum when the ratio of salt/acid or base is 1 (4) the number of moles of acid or base required by one litre of buffer solution to alter its \(\mathrm{pH}\) by one unit is called buffer efficiency
Problem 99
Which of the following mixture can act as a buffer solution? (1) I litre of \(0.2 \mathrm{~N} \mathrm{CH}_{3} \mathrm{COOH}+1\) litre of \(0.2 \mathrm{~N} \mathrm{NaOH}\) (2) I litre of \(0.1 \mathrm{~N} \mathrm{CH}_{3} \mathrm{COOH}+1\) litre of \(0.2 \mathrm{~N} \mathrm{NaOH}\) (3) 1 litre of \(0.2 \mathrm{~N} \mathrm{CH}_{3} \mathrm{COOH}+1\) litre of \(0.1 \mathrm{~N} \mathrm{NaOH}\) (4) All the above
Problem 101
When acid is added to a buffer solution composed of a weak base (B) and its salt with strong acid, then the reaction which occur to maintain the \(\mathrm{pH}\) is (1) \(\mathrm{B}+\mathrm{H}_{3} \mathrm{O}^{+} \longrightarrow \mathrm{BH}^{+}+\mathrm{H}_{2} \mathrm{O}\) (2) \(\mathrm{OH}^{-}+\mathrm{BH}^{+} \longrightarrow \mathrm{B}+\mathrm{H}_{2} \mathrm{O}\) (3) \(\mathrm{B}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{BH}^{-}+\mathrm{OH}^{-}\) (4) \(\mathrm{BH}^{+}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{B}+\mathrm{H}_{3} \mathrm{O}^{+}\)
Problem 110
The \(\mathrm{p} K_{\mathrm{a}}\) of certain weak acid is \(4.0 .\) What should be the salt to acid ratio if we have to prepare a buffer with \(\mathrm{pH}=5\) using the acid and of its salts? (1) \(4: 5\) (2) \(5: 4\) (3) \(10: 1\) (4) \(1: 10\)
Problem 116
The alkali not suitable for volumctric dctermination of IICl using phenolphthalcin as an indicator (1) \(\mathrm{NaOH}\) (2) \(\mathrm{Ba}(\mathrm{OH})_{2}\) (3) \(\mathrm{KOH}\) (4) \(\mathrm{NH}_{4} \mathrm{OH}\)
Problem 119
An universal indicator (1) consists of a single indicator which changes colour at different \(\mathrm{pH}\) ranges (2) consists of a number of indicators which give different colours at different \(\mathrm{pH}\) ranges (3) is used only in the \(\mathrm{pH}\) range of 0 to 7 (4) is used only in the \(\mathrm{pH}\) range of 7 to 14
Problem 120
The colour change of an acid-base indicator is due to the formation of (1) Benzenoid structure (2) Quinonoid structure (3) Ionic structure (4) Covalent bond
