1. When using the equation P1/T1 = P2/T2to relate temperature and pressure of a gas, what must be held constant?2. A sample of gas is held in a capped flask. At 25 °C the pressure is 693 mmHg. What is the pressure of the gas at 37 °C?3. If the heat of vaporization of water is 40.7 kJ/mol, how much energy is required to vaporize 5.0 g of liquid water at 100 °C?4. Would you expect most of the components in a perfume to have a low or high vapor pressure? Explain

1.

P1/T1 = P2/T2

Charles' law states that the pressure of a gas on its containing vessel must be directly proportional to the absolute temperature at constant volume STP.

2.

Using P1/T1 = P2/T2

T1 = 25 °C

= 273 + 25

= 298 K

P1 = 693 mmHg

T2 = 37 °C

= 273 + 37

= 310 K

P2 = (693 * 310) / 298

= 720.9 mmHg.

3.

q = n * Hvap

Where,

q = heat required

n = number of moles

Hvap = heat of vapourisation

Molar mass of H2O = (1*2) + 16

= 18 g/mol

Number of moles = mass/molar mass

= 5/18

= 0.28 mol.

q = 0.28 * 40.7

= 11.3 kJ.

4.

Volatility is defined as a property of a substance which describes how readily a substance vaporizes. At a particular temperature and pressure, a substance with high volatility (high vapour pressure) is more likely to exist as a vapor, while a substance with low volatility (low vapour pressure) is more likely to be a liquid or solid.

Most perfume components exist individually as gas so they have high vapour pressure.