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GATE 2025 CH – Question 40

Mass Transfer · Leaching, liquid-liquid extraction, drying, humidification and adsorption · 2 marks · Multiple choice

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

  1. 7
  2. 14
  3. 28
  4. 18

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Correct answer: (B) 14

Explanation

The phenol removed from the solution is $(100 - 30) \times 0.1 = 7$ mg. It is adsorbed by 0.5 g of adsorbent, so the loading is $\frac{7}{0.5} = 14$ mg per gram.