Question

Assertion: \[HC{O_3}^ - \] can act as a Bronsted acid or Bronsted base.
Reason: \[HC{O_3}^ - \] can donate a proton to form \[C{O_3}^{2 - }\] or accept a proton to form \[{H_2}C{O_3}\] .
A.Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
B.Both Assertion and Reason are correct and Reason is not the correct explanation for Assertion.
C.Assertion is correct but reason is incorrect.
D.Both Assertion and Reason are incorrect.

Answer 1

Hint: Bronsted acid is a substance which has a tendency to donate a proton to any other substance. Bronsted base is a substance which has a tendency to accept a proton from any other substance.

Complete step by step answer:
Lowry and Bronsted concept of acids and bases is applied to aqueous as well as non-aqueous solutions.
According to this concept, an acid has a tendency to donate a proton and base has a tendency to accept a proton from any other substance.
When acid loses a proton, the remaining part has a tendency to regain the proton. So, it behaves as a base. Similarly, when a base accepts a proton, the remaining part has a tendency to lose a proton. So, it behaves as an acid. Such pairs of substances are known as conjugate acid- base pairs.
Eg: \[C{H_3}COOH + {H_2}O\] \[{H_3}{O^ + } + C{H_3}CO{O^ - }\]
         (Acid) (Base) (Acid) (Base)
Here, Acetic acid donates a proton to water and thus acts as an acid. Water accepts a proton therefore, acts as a base. In reverse reaction, \[{H_3}{O^ + }\] donates a proton to the acetate ion and acts as an acid, Thus, acetic acid is the conjugate acid of acetate ion and acetate ion is the conjugate base of acetic acid. Similarly, water acts as the conjugate base of hydronium ion and hydronium ion acts as the conjugate acid of water.

 \[HC{O_3}^ - + {H^ + }\] \[{H_2}C{O_3}\] (Bronsted base)
Here HCO3- accept a proton thus acting as a Bronsted base.
\[HC{O_3}^ - \] \[C{O_3}^{2 - } + {H^ + }\] (Bronsted acid)
Here \[HC{O_3}^ - \] loses a proton thus acts as a Bronsted acid.
From equation we can see that \[HC{O_3}^ - \] can a accept a proton to form \[{H_2}C{O_3}\] and loses a proton to form \[C{O_3}^{2 - }\] . It can act as a Bronsted acid as well as Bronsted Base.
Hence, the correct answer Is (A) i.e Both Assertion and Reason are Correct and Reason is the Correct explanation for Assertion.

Note: According to Lowry- Bronsted concept, the strength of an acid depends upon its tendency to lose protons and the strength of a base depends upon its tendency to gain protons. HCl acts as a strong acid i.e it has a strong tendency to donate protons. Acetic acid is a weak acid, it has less tendency to donate protons.