GATE 2025 Chemical Engineering, Q40 · Mass Transfer
The correct answer is B, 14.
Question
500 mg of a dry adsorbent is added to a beaker containing 100 mL solution of concentration 100 mg phenol/(L solution). The adsorbent is separated out after 5 h of rigorous mixing. If the residual concentration in the solution after separating the adsorbent is 30 mg phenol/(L solution), the amount of phenol adsorbed (in mg per gram of dry adsorbent) is
Official answer: 14
Why
GATE 2025 official key: (B). Phenol adsorbed = (100−30) mg/L L = 7 mg, over 0.5 g adsorbent = 7/0.5 = 14 mg/g.
Explanation cross-checked for consistency. Final answer matches the official IIT answer key.