lonic Equilibrium pH of a Buffer When an acid or a base is

Last updated: 6/28/2023

lonic Equilibrium pH of a Buffer When an acid or a base is added We have just discussed that addition of H ions or OH ions to an acidic buffer HA A does not appreciably changes the pH of buffer Similarly we can analyse the same for a basic buffer BOH B In actual pH of a buffer solution changes by a small quantity Let us calculate this change in pH quantitatively Consider an acidic buffer HA A where salt A and acid HA An acidic buffer is rich in A ions Let us add x mole per litre of HCI to it This added HCI H reacts with A salt to ge undissociated acid as H A salt After adding x M H ions salt x HA acid acid x Now using Henderson s Equation pH original buffer pK log101 pH of buffer decreases Change or difference in pH pH new pH original OH HA acid salt acid Vidyamandir Classes salt x and pH new pK 1 Let us add x M NaOH to the buffer This added NaOH OH ions react with acid HA to produce salt and H O A H O salt pH of buffer increases log10 After adding x M OH ions acid x salt x pH new pK log10 acid x Change in pH pH new pH original Note 1 In exactly similar manner we can calculate the change in pH of a basic buffer BOH B Try to get a relation like this for basic buffer Remember it is not to be used as standard result salt 1 acid 1 ii A buffer solution is assumed to be destroyed if on addition of strong acid or base its pH changes by 1 unit i pH new pK 1 if the initial pH of the buffer solution was pK This means the ratio salt 10 or acid OR base ille Ho b SO