Question

An athlete is given $100g$ of glucose $\left(C_6{H}_{12}{O}_6\right)$ of energy equivalent to $1560kJ$. He utilises $50\%$ of this gained
energy in the event. In order to avoid storage of energy in the body, calculate the weight of water he would need to perspire.
The enthalpy of evaporation of water is $44kJ/mol$

• A. 319
• B. 428
• C. 120
• D. 500

Answer 1

The correct option is A 319

Total energy intake = 1560 kJ
Energy utilised in the event $=0.5\times 1560=780kJ$
Energy to be released due to perspiration to avoid storage =1560-780=780KJ
The enthalpy of evaporation of water = 44 kJ/mol
Moles of water evaporated $=780/44=17.727moles$
Mol. wt. of water= 18 g/mol
Thus mass of water evaporated $=18\times 17.727g=319.086g\cong 319g$
Thus (a) is the correct answer.