Question

An intimate mix of ferric oxide and Al is used as solid rocket fuel. Calculate the fuel value per gm and fuel value per CC of the mix. Enthalpy of formation & densities are: ΔH°f (Al2O3) = -399k cal/mole; ΔH°f (Fe2O3) = -399k cal/mole; Density of Fe2O3 = 5.2 g/cc; density of Al = 2.7 g/cc.

Answer 1

The thermite reaction between aluminum (Al) and iron(III) oxide (Fe2O3) releases a significant amount of heat. To calculate the fuel value per gram or per cc, one needs the correct enthalpy change and densities for a precise calculation.

Step-by-step explanation:

The thermite reaction involves a mixture of aluminum (Al) and iron(III) oxide (Fe2O3). This exothermic reaction can be represented by the thermochemical equation:

2 Al(s) + Fe2O3(s) → 2 Fe(s) + Al2O3(s) + heat

In order to calculate the fuel value per gram and the fuel value per cc of the mix, one would need to know the stoichiometry of the reaction and use the given enthalpy changes. However, the question provides conflicting information regarding the enthalpy change of formation (ΔH°f) for Al2O3 and Fe2O3 (both given as -399 k cal/mole) and a separate overall enthalpy for the reaction. Therefore, without a clear understanding of which values to use, a precise calculation cannot be performed. Additionally, the densities of aluminum and iron(III) oxide are required to convert between mass and volume. If we were provided with a balanced chemical equation and the correct ΔH for the reaction, we could use the stoichiometric relationships to determine the energy per gram and per cc.