Question

What is the delta H when 72.0 grams H2O condenses at 100.00C?

Answer 1

Answer: The value of $\Delta H$ is -163 kJZ

Explanation:

The number of moles is defined as the ratio of the mass of a substance to its molar mass. The equation used is:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$ ......(1)

We are given:

Given mass of water = 72.0 g

Molar mass of water = 18 g/mol

Putting values in equation 1, we get:

$\text{Moles of water}=\frac{72.0g}{18g/mol}\\\\\text{Moles of water}=4mol$

Calculating the heat released for the condensation process:

$\Delta H=n\times \Delta H_{(vap)}$ ......(2)

where,

$\Delta H$ = amount of heat released

n = number of moles of water = 4 moles

$\Delta H_{(vap)}$ = specific heat of vaporization = -40.7 kJ/mol

Negative sign represents the amount of heat released.

Putting values in equation 2:

$\Delta H=4mol\times (-40.7kJ/mol)=-163kJ$

Hence, the value of $\Delta H$ is -163 kJ