Answer:
The heat that must be supplied is 298.1 kJ
Explanation:
We must apply the calorimetry formula to solve this.
Q = m . C . ΔT
where Q is heat, m is the mass, C is the specific heat and ΔT the difference between Final temperature and Initial temperature.
The normal boiling point of water is 100° so ΔT = (100° - 20°)
Notice that units in specific heat are J/ g.K so temperature should be in K but in this case K and C are the same, because it is a difference.
T°K = T°C + 273
ΔT = (100° - 20°) = 80°
ΔT = (373° - 293°) = 80°
750g . 0.51 J/gK . 80K + 800g . 4.18 J/gK . 80K = 298120 J
