Question

The molar heat of vaporization of hydrogen fluoride (HF) is 31.18 kJ/mol. How much heat is released when 100.0 g HF condenses at its boiling point?

Answer 1

the answer is -155.8

Answer 2

Answer: The amount of heat released is 155.9 kJ

Explanation:

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

We are given:

Given mass of HF = 100.0 g

Molar mass of HF = 20 g/mol

Putting values in above equation, we get:

$\text{Moles of HF}=\frac{100.0g}{20g/mol}=5mol$

To calculate the heat of the reaction, we use the equation:

$\Delta H_{rxn}=\frac{q}{n}$

where,

$q$ = amount of heat released =

n = number of moles = 5 moles

$\Delta H_{rxn}$ = enthalpy change of the reaction = 31.18 kJ/mol

Putting values in above equation, we get:

$31.18kJ/mol=\frac{q}{5mol}\\\\q=(31.18kJ/mol\times 5mol)=155.9kJ$

Hence, the amount of heat released is 155.9 kJ