Question

How much heat energy is required to melt 75g of ice at 0°C?

a. 4.45J

b. 30.13J

c. 169, 500J

d. 25, 050J

Answer 1

The enthalpy change for melting ice is called the entlaphy of fusion. Its value is 6.02 kj/mol. This means for every mole of ice we melt we must apply 6.02 kj of heat. We can calculate the heat needed with the following equation:

Q = N x ΔH

where:

Q = heat

N = moles

ΔH = enthalpy

In this problem we would like to calculate the heat needed to melt 35 grams of ice at 0 °C. This problem can be broken into three steps:

1. Calculate moles of water

2. multiply by the enthalpy of fusion

3. Convert kJ to J.

Step 1 : Calculate moles of water

`[ 75g ] x ((1 mol)/(18.02g) ) =`

Step 2 : Multiply by enthalpy of fusion

Q = N × ΔH = [ Step 1 Answer ] × 6.02 =

Step 3 : Convert kJ to J

`[ Step 2 Answer ] x ((1000j)/(1kJ) ) =`

Finally rounding to 2 sig figs (since 34°C has two sig figs) we get

Q Would Equal ____