GATE 2016 ME (ME3) – Question 55
In a mixture of dry air and water vapor at a total pressure of 750 mm of Hg, the partial pressure of water vapor is 20 mm of Hg. The humidity ratio of the air in grams of water vapor per kg of dry air (gw/kgda) is __________
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Correct answer: 16.9 to 17.1
Explanation
Humidity ratio is w=0.622p_v/(p−p_v). The common mmHg units cancel, giving w=0.622×20/(750−20)=0.0170411kg/kg dry air. Multiply by1000 to obtain **17.0411g/kg dry air**. Total mixture mass is not the denominator.