NEETChemistryp Block Elements (Group 15, 16, 17 & 18)
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Addition of MnO ₂ to a heated mixture of NaCl and concentrated H ₂ SO ₄ changes the evolved gas from a greenish-yellow gas to a colourless, pungent-smelling gas. Reason (R): In this reaction, MnO ₂ acts as an oxidising agent and oxidises chloride ions to chlorine gas. In the light of the above stat
Options
- ABoth (A) and (R) are correct and (R) is the correct explanation of (A).
- BBoth (A) and (R) are correct but (R) is not the correct explanation of (A).
- C(A) is correct but (R) is incorrect.
- D(A) is incorrect but (R) is correct.
Correct answer
D. (A) is incorrect but (R) is correct.
Step-by-step solution
Heating NaCl with concentrated H ₂ SO ₄ alone produces hydrogen chloride ( HCl ) gas, which is a colourless, pungent-smelling gas: NaCl + H ₂ SO ₄ NaHSO ₄ + HCl When MnO ₂ is added to this mixture, it acts as an oxidising agent and oxidises the chloride ions to chlorine ( Cl ₂ ) gas, which is greenish-yellow in colour: 2 NaCl + MnO ₂ + 2 H ₂ SO ₄ Na ₂ SO ₄ + MnSO ₄ + 2 H ₂ O + Cl ₂ Thus, the addition of MnO ₂ changes the evolved gas from a colourless, pungent-smelling gas ( HCl ) to a greenish-yellow gas ( Cl ₂ ).