Question

which of the following yields a buffer solution when equal volumes of the two solutions are mixed?   A.) 0.10M HCl and 0.10M NaCl B.) 0.15M HNO3 and 0.15M NaNO3 C.) 0.10M HF and 0.10M NaF D.) 0.10M HClO4 and 0.10M NaClO4 E.) 0.15M HBr and 0.15M NaBr

Answer 1

Of the given combinations, C) 0.1 M HF and 0.1 M NaF would yield a buffer.

Explanation : A buffer solution is defined as a solution which resists any change in its pH value that is whose pH remains practically constant even when small amounts of acid or base are added to it.

There are two types of buffer solutions:
(a) solution of single substances --> the solution of a weak acid and a weak base.. for example ammonium acetate (CH3COONH4) act as a buffer.
(b)solution of mixtures--> these are further of two types..
i) acidic buffer ---> it is the solution of weak acid and a salt of this weak acid with a strong base ..for example--CH3COOH + CH3COONa....here CH3COOH is a weak acid and CH3COONa is a salt of weak acid (CH3COOH) and strong base(NaOH)
ii) basic buffer --->it is the solution of a mixture of weak acid and a salt of this weak base with a strong acid ...for example - NH4OH + NH4Cl ...here NH4OH is a weak base and NH4Cl is a salt of weak base (NH4OH) and strong acid (HCl)..

A) 0.10M HCl and 0.10M NaCl : will not form buffer as HCl is a strong acid and NaCl is neutral because its a salt of strong acid (HCl and strong base (NaOH) so the solution is mostly acidic and cannot neutralize any added acid acid so no buffer ability.

B) 0.15M HNO3 and 0.15M NaNO3 : HNO3 is a strong acid, and will not form buffer.

C) 0.10M HF and 0.10M NaF : Will form buffer. HF is a weak acid and NaF is a salt of weak acid. The combination thus will form buffer.

D) 0.10M HClO4 and 0.10M NaClO4 : Will not form buffer. The combination NaClO4 and HClO4 is not one of an acid-base buffer, because HClO4 is one of the very strongest strong acids.

E) 0.15M HBr and 0.15M NaBr : Will not form buffer. HBr is a strong acid and thus does not qualify to form buffer solution.