Question

Use 120 and 140 degrees Celsius and calculate the ΔHvap in kJ/mol. Report your answer to 3 sig figs.

a) 20 kJ/mol
b) 250 kJ/mol
c) 30 kJ/mol
d) 40 kJ/mol

Answer 1

The enthalpy change of vaporization (ΔHvap) can be calculated using the formula ΔHvap = q/m, where q is the heat absorbed by the substance and m is the amount of substance in moles. First, calculate the heat absorbed using the formula q = C * ΔT, where C is the heat capacity and ΔT is the change in temperature. Then, calculate ΔHvap by dividing q by the amount of substance in moles. Finally, round the answer to 3 significant figures.

Step-by-step explanation:

The enthalpy change of vaporization (ΔHvap) can be calculated using the formula:

ΔHvap = q/m

Where q is the heat absorbed by the substance and m is the amount of substance in moles.

First, we need to calculate the heat absorbed using the formula:

q = C * ΔT

Where C is the heat capacity and ΔT is the change in temperature.

For the given temperatures of 120 and 140 degrees Celsius, the change in temperature is 20 degrees Celsius.

Let's assume the heat capacity is 5 J/mol.°C for simplicity.

q = 5 J/mol.°C * 20 °C = 100 J/mol

Next, we can calculate the enthalpy change of vaporization:

ΔHvap = q/m = 100 J/mol / 1 mol = 100 J/mol

To convert the answer to kJ/mol, we divide it by 1000:

ΔHvap = 100 J/mol / 1000 = 0.1 kJ/mol

Rounding to 3 significant figures, the answer is 0.100 kJ/mol.