NEET UG 2008 — Chemistry Organic Chemistry

$\begin{aligned} & \mathrm{C}_5 \mathrm{H}_{12(g)}+8 \mathrm{O}_{2(9)} \longrightarrow 5 \mathrm{CO}_{2(g)}+6 \mathrm{H}_2 \mathrm{O}_{(\mathrm{e})} \\ & \therefore \Delta \mathrm{G}_r=5\left(\Delta \mathrm{G}_r\right)_{\mathrm{CO}_2}+6\left(\Delta \mathrm{G}_{\mathrm{r}}\right)_{\mathrm{H}_2 \mathrm{O}}-\left(\Delta \mathrm{G}_{\mathrm{r}}\right)_{\text {Pentane }} \\ & =5(-5394.4)+6(-237.2)-(-8.2) \\ & =-1972-1423.2+8.2 \\ & \Delta \mathrm{G}_{\mathrm{R}}=-3387 \mathrm{~kJ} / \mathrm{mole} \\ & \mathrm{C}_5^{\frac{-12}{5}} \mathrm{H}_{12} \longrightarrow 5 \stackrel{4}{\mathrm{C}_2} \end{aligned}$​C5​H12(g)​+8O2(9)​⟶5CO2(g)​+6H2​O(e)​∴ΔGr​=5(ΔGr​)CO2​​+6(ΔGr​)H2​O​−(ΔGr​)Pentane ​=5(−5394.4)+6(−237.2)−(−8.2)=−1972−1423.2+8.2ΔGR​=−3387 kJ/moleC55−12​​H12​⟶5C2​4​​ For 5 carbon atoms, there is a change of electrons from - 12 to 20 $\begin{aligned} & \therefore \text { No. of electrons involved }=32 \mathrm{e}^{-} \\ & \Delta G_r=-3387 \times 10^3=-32 \times E^{\circ} \times 96500 \\ & E^{\circ}=1.097 V \end{aligned}$​∴ No. of electrons involved =32e−ΔGr​=−3387×103=−32×E∘×96500E∘=1.097V​