What is the ratio of methanol to water vapor in the gas phase at 40°C for a 10% methanol aqueous solution?
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What is the ratio of methanol to water vapor in the gas phase at 40°C for a 10% methanol aqueous solution?
Check the vapor pressure by using Raoult’s law
Give Dalton’s law of partial pressures and Raoult’s law a try.
Is it to check the saturated vapor pressures of methanol and water at that temperature respectively? Then in the gas phase, is the ratio of methanol to water in an ideal state equal to the ratio of their saturated vapor pressures? ? I hope the expert can give some guidance!
Is it to check the saturated vapor pressures of methanol and water at that temperature respectively? Then in the gas phase, is the ratio of methanol to water in an ideal state equal to the ratio of their saturated vapor pressures? ? I hope the expert can give some guidance!
No, in addition to checking the vapor pressure, it is also necessary to perform calculations using Raoult’s law formula; once you look up that formula, you’ll understand
How is it calculated? ? Thank you!
The molar fractions are calculated based on weight percentages. The saturated vapor pressures of water and methanol at 40°C are looked up, and assuming the system is an ideal solution, the partial pressure of each component is equal to its saturated pressure multiplied by its molar fraction. . .
The saturated vapor pressure of water at 40°C is 7.5 KPa, while that of methanol is 35.36188 KPa.
The saturated vapor pressure of water at 40°C is 7.5 KPa, while that of methanol is 35.36188 KPa. Assuming the solution weighs 1 KG, then 100 g of methanol corresponds to 3.125 moles. 900 g of water = 50 mol. The molar fraction of methanol is 0.05882, while that of water is 99.94118. As per Raoult’s law ； P(methanol) = P(pure methanol) × mole fraction of methanol = 35.36188 × 0.05882 = 20.7978578 KPa. P(hydrogen water) = P(pure water) × mole fraction of water = 7.5 × 99.94118 = 749.558824 KPa. The ratio of partial pressures is equal to the ratio of mole numbers. ) Therefore, the ratio of moles = P(methanol) / P(water) = 20.7978578/749.558824 = 0.0277494886