Answer to Question #252239 in Quantum Mechanics for felice

Question

.Evander took out 1 L of water from the refrigerator, when he measured the temperature of the water it showed that the water was at 10 oC. Evander thinks that it is still too cold so he adds 500 g of hot water. The temperature of the new mixture becomes 30 oC. What is the temperature of the hot water?

Assume that the specific heat of the water is 4.2 J/g oC.
1 Liter of water equal to 1000 grams

Answer 1

Write the equation of thermal equilibrium:

$$Q_\text{cold}+Q_\text{hot}=0,\\ cm_c\Delta t_c+cm_h\Delta t_h=0,\\ 4200·1(30-10)+4200·0.5(30-T)=0,\\\space\\ T=70°\text{C}.$$