Topic: Thermodynamics
For water, the latent heat of freezing is 334 kJ/kg and the specific heat capacity averages 4.19 kJ/kgK. The quantity of heat to be removed from 1 kg of water at 30 °C in order to turn it into ice at 0 °C is:
- A. 567 kJ
- B. 319 kJ
- C. 483 kJ
- D. 459 kJ
Answer: D. 459 kJ
Explanation: Total heat removed Q = Sensible heat + Latent heat. Sensible heat to cool water from 30 °C to 0 °C = m * C * dT = 1 * 4.19 * 30 = 125.7 kJ. Latent heat to freeze = m * L = 1 * 334 = 334 kJ. Total Q = 125.7 + 334 = 459.7 kJ, which is approximately 459 kJ.