Question

How many joules does it take to melt 35 g of ice at ${{0}^{o}}C$ ?

Answer 1

There is a formula to calculate the energy required to melt some amount of ice and it is as follows.
$q=n\times \Delta H$
Here q = amount of heat
n = number moles of water
$\Delta H$ = change in enthalpy

Complete step-by-step answer: - In the question it is asked to calculate the number of joules required to melt 35 g of ice at ${{0}^{o}}C$ .
- The data given in the question is 35 g of ice at ${{0}^{o}}C$.
- The formula to calculate the energy to melt the 35 gm of ice is as follows.
$q=n\times \Delta H$
Here q = amount of heat
n = number moles of water
$\Delta H$ = change in enthalpy
- First we have to calculate the number of moles of water from the given data.
- The number of moles of water for 35 g of ice is as follows.
$\text{number of moles for 35 g of water = }\dfrac{35}{18}=1.94moles$
- Means we have to calculate the energy required to melt 1.94 moles of the water.
- The enthalpy of fusion of water = 6.02 kj/mol.
- Substitute all the known values in the above formula to get the number of joules required.

$$q=n\times \Delta H \\\ q=1.94\times 6.02 \\\ q=11.678kJ \\\$$

- We got the answer in kilojoules. We have to convert the heat into joules.
11.678 kJ = 11,678 J.
- Therefore the amount of heat required in joules to melt the ice at ${{0}^{o}}C$ is 11,678 joules.

Note: We have to calculate the number of moles of water from the given data then only we will get the heat required and we also should know the value of enthalpy of fusion for ice. Without knowing these two we cannot find the amount of heat required.