It is observed that the functioning of neuronal circuits in our brain is driven by the energy available from the combustion of glucose. Calculate the amount of glucose (in gm) which should be burnt per hour to produce sufficient energy for the brain, which operates at $\frac{128}{9}$ watts.
Given : $| Δ H^{0} |$ of combustion of glucose at 400 K = $3000$ kJ/mol
$| Δ S^{0} |$ of combustion of glucose at 400 K= $180$ J/mol K

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Solution

$C_{6} H_{12} O_{6} (s) + 6 O_{2} (g) \to 6 C O_{2} (g) + 6 H_{2} O (g)$
$Δ G^{0} = Δ H^{0} - T Δ S^{0}$
Useful energy $= - 3000 - 400 \times 0.18$ $= - 3072 k J / m o l$

Energy required per hour $= \frac{128}{9} \times 60 \times 60 J$
$∴$ Glucose needed per hour $=$ $\frac{\frac{128}{9} \times 60 \times 60}{3072 \times 1000} m o l = \frac{\frac{128}{9} \times 60 \times 60}{3072 \times 1000} \times 180 g = 3 g$

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