Question

Consider a buffer made with benzoic acid and sodium benzoate

a). Write the neutralization reaction that would occur if a small amount of HCL is added to the buffer system.

b). Write the neutralization reaction that would occur if a small amount of NaOH is added to the buffer system.

Answer 1

Buffer reactionss:

C6H5COOH <------> C6H5COO- + H+ (weak dissociation)

C6H5COONa ------> C6H5COO- + Na+ (strong dissociation)

when you addsmall amount of HCl then,

HCl -----> H+ + Cl-

H + (from acid) + C6H5COO- (from BUffer) -------> C6H5COOH

so the H+ ion concentration is neutralised by the buffer solution hence pH of the solution is not changed.

When you add small amount of Base NaOH then,

NaOH -----> Na+ + OH-

OH- (from base) + C6H5COOH (from buffer) --------> C6H5Coo- + H2O

so the OH- ion concentration is neutralised by the buffer solution hence pH of the solution is not changed.