CGPET 2013 Solved Paper

A buffer solution can be described as a solution, which will resist changes in $\mathrm{pH}$ when a small amount of a strong acid or base is added.An acidic buffer is compound of a weak acid and its conjugated base or a weak acid and the salt of the weak acid and a strong base. e.g.,$(\mathrm{CH}_3\mathrm{COOH}+\mathrm{CH}_3\mathrm{COONa})$.$\;\mathrm{CH}_3\mathrm{COOH} ightleftharpoons \mathrm{CH}_3\mathrm{COO}^{-}+\mathrm{H}^{+}\;$$\;\;\text{(feebly ionised)}\;$$\;\mathrm{CH}_3\mathrm{COONa} ightleftharpoons \mathrm{CH}_3\mathrm{COO}^{-}+\mathrm{Na}^{+}$(completely ionised)How to make a acidic buffer(i) Start with taking weak acid $(\mathrm{CH}_3\mathrm{COOH})$ and strong base $(\mathrm{NaOH})$ in 2 : 1 molar concentration ratio, sothat a sufficient number of moles of the $\mathrm{CH}_3\mathrm{COOH}$ nutralize completely the same number of moles of $\mathrm{NaOH}$.(ii) The acidic buffer can also be prepared by taking equimolar concentrations and volume of weak acid $(\mathrm{CH}_3\mathrm{COOH})$ and the salt of the weak acid and strong base $(\mathrm{CH}_3\mathrm{COONa})$.