3. In your experimental calculations, we did not correct for the vapor pressure

Question

3. In your experimental calculations, we did not correct for the vapor pressure of the water. generated from an aqueous solution or that occupies space above an aqueous solution will also contain water vapor. P(total measured pressure) = P(water vapor) + P(gas) Look up the vapor pressure of water at the temperature of the experiment. Explain how including this correction would affect your overall answer for the molar volume calculation and the molar mass of CO2 calculation. Experiment 11 Page 11

Explanation / Answer

3. Determination of molar volume of a gas

molar volume = volume of gas at STP/moles of gas produced

volume of gas at STP = P1.V1.T2/T1.P2

where,

P1, V1 and T1 are Pressure, volume and temperature, respectively of gas at temperature of experiment

P2 and T2 are pressure and temperature at STP conditions

So,

as can be seen, volume of gas at STP is directly proportional to the pressure of gas calculated

So, if the correction of water vapor pressure is not done from the overall pressure, the net pressure of gas calculated would be higher than actual gas pressure. So the volume of gas at STP would be higher.

Therefore, the molar volume would also be obtained much greater than the actual value.

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