Identify the Bronsted-Lowry acid-base pair in the following equation:

HCN + NO2- ⇌ CN- + HNO2

      HCN    +       NO₂⁻        ⇌               CN⁻            +          HNO₂

Weak acid     Strong base        Conj. strong base      Conj. weak acid

Explanation:

In the Bronsted-Lowry theory we identify the acids as the compounds that can release protons and the bases, the compounds that can accept them.

For example:

HCl → It can release the proton → Acid → Hydrochloric acid

NH₃ → It can accept a proton → Base → Ammonia

The equation is:

HCN + NO₂⁻ ⇌ CN⁻ + HNO₂

Cianhydric acid release a proton (acid) to the nitrite (base).

Nitrite can accept the proton (base) to become nitrous acid.

Then, the cianide can also accept the proton (base) to become cianhydric acid, again.