How much energy is need to raise 50 kg of water from 45 degrees c to 80 degrees c

Energy = mass * specific heat capacity*change in temperature'

In this case, the mass of water is 50 kg, the specific heat capacity of water is 4184J/kg

the change in temperature is 80-45 = 35 degrees celcius

Therefore, heat energy

= 50 * 35 * 4184=7322000 Joules

But 1kJ = 1000 Joules

therefore, the energy needed will be 7322 kJ