Question

how much heat energy is necessary to raise the temperature of 3kg of water from 30°C to 40°C ?
1. 30 cal
2. 300 cal
3. 30 kcal
4. 300 kcal​

Answer 1

Answer:

Assuming that the water at 100C is liquid water (not boiled), then we can say:

ΔH = m•Cp•ΔT where H is enthalpy (heat), m is mass Cp is heat capacity and ΔT is temperature change.

The heat capacity of water is dependent on temperature, but is commonly taken as 4.186kJ/kg-K

In this case, we have 10kg of water and a temperature change ΔT = 70K

So ΔH = 10(4.186)(70) = 2930.2kJ

The heat required is 2930.2kJ (which is 0.814kWh)

If the 10kg were boiled (vaporized) off at 100C, it’s a whole different ball game:

The enthalpy of vaporization of water is 2256.4kJ/kg

So 10kg requires ΔH = 10(2256.4) = 22,564kJ (which is 6.27kWh)

Explanation:

i hope it's helpful for you