Question

Calculate the standard heat of formation of liquid hexane, C6H14(1), using the standard heats of combustion given below: \left.C_{6} H_{14}(l)+\frac{19}{2} \mathrm{O}_{2}(g) \rightarrow 6 \mathrm{CO}_{2}(g)+7 \mathrm{H}_{2} \mathrm{O(l}\right) \quad \Delta \widehat{\mathrm{H}}_{c}^{o}=-4163.1(\mathrm{~kJ} / \mathrm{mol}) C(s)+O_{2}(g) \rightarrow C O_{2}(g) \quad \Delta \widehat{H}_{c}^{o}=-393.51(k J / m o l) \mathrm{H}_{2}(g)+\frac{1}{2} \mathrm{O}_{2}(g) \rightarrow \mathrm{H}_{2} \mathrm{O}(l) \quad \Delta \widehat{\mathrm{H}_{c}^{o}}=-285.84(\mathrm{~kJ} / \mathrm{mol}) The reaction of ammonia with oxygen to form nitrogen dioxide and steam is given below: 4 N H_{3}(g)+7 O_{2}(g) \rightarrow 4 N O_{2}(g)+6 H_{2} O(g) Calculate the standard heat of reaction for the above reaction. The standard heats of formation for NH3(g), NO2(g), and H20(1) as well as the heat of vaporisation for water at 100°C and 1 atm are given below (the heat capacity formulas are available in Table Q4 on page 5).[7 marks] \frac{1}{2} N_{2}(g)+\frac{3}{2} H_{2}(g) \rightarrow N H_{3}(g) \quad \Delta \widehat{H}_{f}^{o}=-46.19(k J / m o l) \frac{1}{2} N_{2}(g)+O_{2}(g) \rightarrow N O_{2}(g) \quad \Delta \widehat{H}_{f}^{o}=33.8(k J / m o l) \mathrm{H}_{2}(g)+\frac{1}{3} \mathrm{O}_{2}(g) \rightarrow \mathrm{H}_{2} O(l) \quad \Delta \widehat{\mathrm{H}_{f}^{o}}=-285.84(\mathrm{~kJ} / \mathrm{mol}) \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightarrow \mathrm{H}_{2} O(g) \quad \Delta \widehat{\mathrm{H}}_{v}\left(100^{\circ} \mathrm{C}, 1 \mathrm{~atm}\right)=40.656(\mathrm{~kJ} / \mathrm{mol}) The reaction equation for combustion of methane with oxygen is given below: \mathrm{CH}_{4}(g)+2 \mathrm{O}_{2}(g) \rightarrow \mathrm{CO}_{2}(g)+2 \mathrm{H}_{2} \mathrm{O}(l) Calculate the HHV for methane and the heat of above combustion at 100°C and1 atm. The standard heats of formation are given below (the heat capacity formulas are available in Table Q4 on page 5).[8 marks] C(s)+2 H_{2}(g) \rightarrow C H_{4}(g) \quad \Delta \widehat{H_{f}^{o}}=-74.85(k J / m o l) C(s)+O_{2}(g) \rightarrow C O_{2}(g) \quad \Delta \widehat{H_{f}^{o}}=-393.5(k J / m o l) \mathrm{H}_{2}(g)+\frac{1}{2} \mathrm{O}_{2}(g) \rightarrow H_{2} O(l) \quad \Delta \widehat{H}_{f}^{o}=-285.84(k J / m o l)

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