In a mixture of dry air and water vapor at a total pressure

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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 (g_w/kg_da) is ________

1. 10 gw/Kgda
2. 17 gw/Kgda
3. 27 gw/Kgda
4. 25 gw/Kgda

Correct Option: B

w = 0.622	P_v
	P_t - P_v

= 0.622 ×		20
		750 - 20

= 0.017 Kgw/Kgda = 17 gw/Kgda