Chapter 10, Problem 66A

Interpretation Introduction

Interpretation: The water that evaporates through perspiration from the body due to two hours of exercise to be calculated. 

Concept introduction: The power to do work or to generate heat is energy. It can be categorize as kinetic energy and potential energy.

Answer to Problem 66A

4867.85 g or 4.87L of water would have to evaporate.

Explanation of Solution

Given heat generated by one hour exercise is 5500kJ.

Thus heat generated by two hours exercise is $\text{55}00\text{kJ}\times \text{2=11000kJ}$ .

Given heat of vaporization of water is $\text{40}\text{.6}\text{kJ}/\text{mol}$ .

Thus 40.6kJ of energy lead to perspiration of 1 mol water.

Therefore, 40.6kJ of energy lead to perspiration of water = 1mol = 18 g water.

1 kJ of energy that lead to perspiration of water is $\frac{\text{18g}}{\text{40}\text{.6}}\text{=0}\text{.44g}$

11000 kJ of energy that lead to perspiration of water is $\frac{\text{18g}}{\text{40}\text{.6}}\times \text{11000=4876}\text{.85g}$

1000 g of water = 1L of water

Thus, 4867.85 g of water = 4.87L of water

Conclusion

4867.85 g or 4.87L of water is would have to evaporate through perspiration rid 11000 kJ of heat generated during two hours of exercise.