Question

Calculate the number of kilojoules to warm 125 g of iron from 23.5 degrees C to 78 degrees C

Answer 1

The heat capacity of iron is 0.45J/g°C.
We calculate the heat using the equation:
ΔH = m cp ΔT
where 
m is the mass
ΔH is enthalphy or the heat required
cp is the heat capacity
ΔT is the change in temperature
So, 
ΔH = m cp ΔT = (125g) (0.45 J/g°C) (75°C - 23.5°C)
ΔH = 2896.875 J

Dividing by 1000 to convert to kJ,
ΔH = 2.897 kJ