Subtopic: Psychrometry – properties of air-water vapour mixture
Question Statement:
Wheat weighing 4900 N at moisture content of 25% on wet basis is to be dried to moisture content of 10% on dry basis. The amount of moisture evaporated from the wheat in kg is
Options:
(A) 87
(B) 103
(C) 116
(D) 156
Official Answer Key:
A
Step-by-Step Solution & Explanation
Initial mass m₁ = W/g = 4900/9.81 = 499.49 kg. Dry matter (bone-dry) mass = m₁(1−MC_wb) = 499.49×0.75 = 374.62 kg. Final MC = 10% on dry basis → MC_wb,final = 0.10/1.10 = 0.0909. Final total mass m₂ = dry matter/(1−MC_wb,final) = 374.62/0.9091 = 412.08 kg. Water removed = m₁ − m₂ = 499.49 − 412.08 = 87.4 kg ≈ 87 kg, matching option (A). Distractors arise from mixing wet/dry-basis conversions inconsistently.
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