NEETChemistryPractical Chemistry
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : Addition of dilute H ₂ SO ₄ to a solid nitrite salt produces a reddish-brown gas. Reason (R) : The reaction initially produces unstable nitrous acid ( HNO ₂ ) which decomposes to yield nitric oxide ( NO ), which is readily oxidised by air to form reddish-brown nitrogen dioxide ( NO ₂ ). In the lig
Options
- ABoth (A) and (R) are true and (R) is the correct explanation of (A)
- BBoth (A) and (R) are true but (R) is not the correct explanation of (A)
- C(A) is true but (R) is false
- D(A) is false but (R) is true
Correct answer
A. Both (A) and (R) are true and (R) is the correct explanation of (A)
Step-by-step solution
Assertion (A) is true. When dilute H ₂ SO ₄ is added to a nitrite ( NO ₂⁻ ) salt, a reddish-brown gas is evolved. Reason (R) is also true and correctly explains (A). The reaction of nitrite with dilute acid produces nitrous acid ( HNO ₂ ). Nitrous acid is unstable and disproportionates to give nitric acid, water, and nitric oxide ( NO ). 3 HNO ₂ HNO ₃ + H ₂ O + 2 NO Nitric oxide ( NO ) is a colourless gas, but it readily reacts with atmospheric oxygen to form nitrogen dioxide ( NO ₂ ), which is a reddish-brown gas.