Chemistry - Ideal Gas Question with Solution | TestHub
ChemistryIdeal GasVapour PressureMedium2 minQB
ChemistryMediuminteger
On a humid evening the air temperature is 27°C and the relative humidity is 75%. The saturation vapour pressure of water is 30.0 mm Hg at 27°C and 8.4 mm Hg at 7°C. If the temperature falls to 7°C overnight and the fraction of the mass of water vapour that condenses out is x, then the value of 1000x is
Answer:
600
Solution:
Initial partial pressure of water vapour: p₁ = 0.75 × 30.0 = 22.5 mm Hg at 300 K. Moles of vapour per unit volume are proportional to p/T: initially 22.5/300 = 0.075. At 7°C (280 K) the air can hold at most the saturated pressure 8.4 mm: 8.4/280 = 0.03. Since 0.03 < 0.075, condensation occurs. Fraction remaining = 0.03/0.075 = 0.4, so fraction condensed x = 1 - 0.4 = 0.6. Hence 1000x = 0600.
Stream:JEESubject:ChemistryTopic:Ideal GasSubtopic:Vapour Pressure
⏱ 2mℹ️ Source: QB
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