Question

Remember the expert uses the numbers in the problem rounded to the correct significant digits. The expert allows plus or minus 3% error in a calculation. So be careful when judging the expert's response. You may be using the correct approach, but have a minor math, substitution, or rounding error.

1) A sample of water in the vapor phase (no liquid present) in a flask of constant volume exerts a pressure of 450 mm Hg at 98 C. The flask is slowly cooled.

a). Assuming no condensation, use the Ideal Gas Law to calculate the pressure of the vapor at 87 C; at 72 C.

b) On the basis of your answers in a) and b), predict the pressure exerted by the water vapor in the flask at 87 C; at 72 C.

2) Consider two closed containers each partially filled with liquid water one at 87 C and the other at 72 C. Can the pressure of water vapor in the gas phase in either container ever exceed the equilibrium vapor pressure at the particular temperature? What is the vapor pressure for water at 87 C and at 72C?

3) Write a chemical equation describing the condensation process for N₂ and a chemical equation describing the freezing process for N₂. For each process discuss the change in enthalpy and entropy that occurs. For each process describe the conditions (in terms of temperature) that support a thermodynamically favorable change, and the conditions that do not support a thermodynamically favorable change.

4) The normal boiling point of methanol is 65.0 C and its Hvap = 37.4 kJ mol-1. Calculate the temperature at which methanol has a vapor pressure of 180.08 mmHg.

Answer 1

The Answers:

IN #1:

We need more information. Although it is said that the bottle is at a constant volume we have no amount either in grams , in mL or density of water vapor to convert a quantity of matter , we have no indication of whether it is possible to use the figure called (volume molar , Vm ) in the absence of the container volume and the number of moles of water vapor as a ratio of those variables (Vm = V / n ) . You can not run a calculation in the absence of these values ??or signs.

IN #2:

We need more information. Although it is said that the bottle is at a constant volume we have no amount either in grams , in mL or density of water vapor to convert a quantity of matter , we have no indication of whether it is possible to use the figure called (volume molar , Vm ) in the absence of the container volume and the number of moles of water vapor as a ratio of those variables (Vm = V / n ) . You can not run a calculation in the absence of these values ??or signs.

IN #3:

Write a chemical equation describing the condensation process for N2

N2(g) -------------> N2(l)

77.35K<T; Sg-l=decreased and Hg-l=increased

Write a chemical equation describing the freezing process for N2

N2(l) -------------> N2(s)

63.14K<T<77.35K; Sl-s=decreased more than Sg-l and Hl-s=increased more than Hg-l

IN #4:

The normal boiling point of methanol is 65.0