If you add 700 kJ of heat to 700 g of water at 70.0°C, how much water is left in the container? The latent heat of vaporization of water is 2.26 × 10⁶ J/kg and its specific heat is is 4190 J/(kg∙K).

Question

Quizplus · Accepted Answer

First, calculate the energy needed to raise the temperature of water from 70°C to 100°C:  Q = mcΔT = 0.7 kg * 4190 J/(kg∙K) * (100°C - 70°C) = 87990 J.  Convert 700 kJ to J: 700 kJ = 700,000 J.  Energy left for vaporization: 700,000 J - 87990 J = 612010 J.  Mass vaporized = Energy left / Latent heat = 612010 J / 2.26 × 10^6 J/kg ≈ 0.271 kg = 271 g.  Initial mass = 700 g, so mass left = 700 g - 271 g = 429 g.

If You Add 700 KJ of Heat to 700 G