The combustion of which fuel provides the most energy per 100 g? A - VCE - SSCE Chemistry - Question 22 - 2020 - Paper 1

To determine the energy released per 100 g of each fuel, we can use the following equation:

ext{Energy (per 100 g)} = ext{Molar mass} imes ext{Energy released per mol} imes rac{100 ext{ g}}{ ext{Molar mass}}

Calculating for each fuel:

1. Pentane:

   • Molar Mass (M) = 72 g mol^-1
   • Energy released = 49097 MJ tonne^-1 = 49097 × 10³ kJ tonne^-1
   • Energy for 100 g = (\frac{49097 \times 10^3}{1000} = 49097 \text{ kJ} ) (as 1 tonne = 1000 kg)

2. Nitromethane:

   • M = 61 g mol^-1
   • Energy released = 11.63 kJ g^-1
   • Energy for 100 g = 11.63 × 100 = 1163 kJ

3. Butanol:

   • M = 74 g mol^-1
   • Energy released = 2670 kJ mol^-1
   • Energy for 100 g = (\frac{100}{74} \times 2670 = 3605.41 \text{ kJ} )

4. Ethyne:

   • M = 26 g mol^-1
   • Energy released = 1300 kJ mol^-1
   • Energy for 100 g = (\frac{100}{26} \times 1300 = 5000 \text{ kJ} )

Conclusion:

To compare:

• Pentane: 49097 kJ
• Nitromethane: 1163 kJ
• Butanol: 3605.41 kJ
• Ethyne: 5000 kJ

Thus, the fuel that provides the most energy per 100 g is nitromethane.