Question

The enthalpy change involved in the oxidation of glucose is -2880 kJ mol${}^{-1}$. Twenty five percent of this energy is available for muscular work. If 100 kJ of muscular work is needed to walk one kilometer, what is the maximum distance that a person will be able to walk after eating 125 g of glucose?

• A. 5 km
• B. 10 km
• C. 7.25 km
• D. 2.25 km

Answer 1

The correct option is A 5 km

As only 25% of the energy is available for muscular work
So,
Energy available for muscular work $=\frac{25}{100}\times 2880=720$ kJ/mol
Molar mass of glucose = 180 g
Moles of glucose in 125 g of glucose = $\frac{125}{180}\text{mol}$

$\therefore$ Energy available for muscular work from 125 g of glucose,
= Moles$\times$ Energy per mole
$=\frac{125}{180}\times 720=500$ kJ
100 kJ of muscular work is needed to walk one kilometer
$\therefore$ Distance travelled $=\frac{500}{100}=5$km.