The standard enthalpies of formation of CO2(g), H2O(l) and glucose(s) at 25°C are – 400 kJ/mol, – 300 kJ/mol and –1300 kJ/mol, respectively. The standard enthalpy of combustion per gram of glucose at 25°C is :

Engineering

Chemistry

Enthalpy of Formation Combustion and Bond

Question

The standard enthalpies of formation of CO₂(g), H₂O(l) and glucose(s) at 25°C are – 400 kJ/mol, – 300 kJ/mol and –1300 kJ/mol, respectively. The standard enthalpy of combustion per gram of glucose at 25°C is :

– 16.11 kJ

–2900 kJ

+ 16.11 kJ

+ 2900 kJ

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C₆H₁₂O₆(s) + 6O₂(g) $\to$ 6CO₂(g) + 6H₂O (l)

${ΔH}_{comb . C_{6} H_{12} O_{6}}^{°} = 6 {ΔH}_{f {CO}_{2}}^{°} + 6 {ΔH}_{f H_{2} O (ℓ)}^{°} - {ΔH}_{f C_{6} H_{12} O_{6} (s)}^{°}$

= 6 × (– 400) + 6 × (– 300) – (– 1300)

= – 2900 kJ/mol

$∴$ Standard enthalpy of combustion per gram of glucose = $\frac{- 2900}{180}$ = – 16.11 kJ