Which one of the following is a buffer solution? A. HCOOH+HCOO−
B. CH3COOH+CH3COO−
C. H2CO−4+C2O2−4
D. H3BO3+BO3−3

A and B are buffer solutions

Explanation:

A buffer is the mixture of a weak base and its conjugate base or vice versa:

Formic acid, HOOH, is a weak acid and its conjugate base is HCOO⁻:

A. HCOOH+HCOO− . Is a buffer.

Acetic acid, CH₃COOH is a weak acid and its conjugate base is CH₃COO⁻:

B. CH₃COOH+CH₃COO− . Is a buffer.

Oxalic acid, H₂CO₄, is a weak acid but its conjugate base is HCO₄⁻.

C. H2CO−4+C2O2−4 . Is not a buffer

Boric acid, H₃BO₃ is a weak acid but its conjugate base is H₂BO₃⁻

D. H₃BO₃ + BO₃³⁻. Is not a buffer.