JEE Main 2026 · 24 January · morning · Single correct · +4 / −1
Consider the following two reactionsA andB.
Numerical value of [molar mass of x+ molar mass of y ] is ____
- (a) 46
- (b) 160
- (c) 88
- (d) 4
Answer and solution
Answer (a) 46
Solution
Chemistry ma’am · 4 steps
Name the gas from each reagent: active metal gives hydrogen, bicarbonate gives carbon dioxide.
- Reaction A. Phenol is weakly acidic, so its O-H hydrogen is replaced by sodium metal. This gives sodium phenoxide and releases hydrogen gas, so x = H₂.
2C₆H₅OH + 2Na → 2C₆H₅ONa + H₂ ↑
- Reaction B. Benzoic acid is a stronger acid than carbonic acid, so it decomposes sodium bicarbonate. The products are sodium benzoate, water and carbon dioxide, so y = CO₂: C₆H₅COOH + NaHCO₃ → C₆H₅COONa + H₂O + CO₂ ↑.
- Add molar masses. H₂ = 2 g mol⁻¹ and CO₂ = 12 + 32 = 44 g mol⁻¹. The sum is 2 + 44 = 46.
- So. The value of [molar mass of x + molar mass of y] is 46, option (a).
The idea to keep. An acid with sodium metal always gives H₂. An acid stronger than carbonic acid with NaHCO₃ gives brisk effervescence of CO₂. Phenol is too weak for the bicarbonate test.
Answer from the NTA final answer key. Solution by PrepWiser.