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Thermodynamics

# Enthalpy change involved in the oxidation of glucose is $-2880\: kJ/mol$. Twenty five percent of this energy is available for muscular work. If $100\: kJ$ of muscular work is required to walk one kilometer, what is the maximum distance that a person will be able to walk after eating $120g$ of glucose.

$\begin {array} {1 1} (A)\;10.8\: km & \quad (B)\;5.4\: km \\ (C)\;4.8\: km & \quad (D)\;3.2\: km \end {array}$

$C_6H_{12}O_6 + 6O_2\rightarrow 6CO_2 + 6H_2O; \: \: \: \Delta H = -2880 \: kJ/mol$
Energy available from $180\: g$ of glucose for muscular work $= 2880 \times \large\frac{25}{100}$$= 720\: kJ Energy available from 120\: g of glucose = 720 \times \large\frac{120}{180}$$ = 480 \: kJ$
Distance travelled from $100\: kJ$ of muscular work = $1\: km$
Distance travelled from $480\: kJ$ of muscular work $= \large\frac{480}{100}$$= 4.8\: km$
Ans : (C)