Question

The reusable booster rockets of the space shuttle use a mixture of aluminum and ammonium perchlorate as fuel. A possible reaction is

3Al (s) + 3NH4ClO4 (s) = Al2O3 (s) + AlCl3 (s) + 3NO (g) 6H2O (g)


Calculate the delta H for this reaction.

Answer 1

ΔH for this reaction : -2668.4 (exothermic)

Further explanation  

The change in enthalpy in the formation of 1 mole of the elements is called enthalpy of formation  

The enthalpy of formation measured in standard conditions (25 ° C, 1 atm) is called the standard enthalpy of formation (ΔHf °)  

(ΔH) can be positive (endothermic = requires heat) or negative (exothermic = releasing heat)  

The value of ° H ° can be calculated from the change in enthalpy of standard formation:  

∆H ° rxn = ∑n ∆Hf ° (product) - ∑n ∆Hf ° (reactants)  

you can search the value of ΔHf on the internet

∆H ° rxn =( ∆H Al₂O₃+∆H AlCl₃+3.∆H NO + 6.∆H H₂O)-(∆H Al+∆H NH₄ClO₄)

$\tt \Delta H^o~rxn=(-1669.8+-704+(3\times 90.4)+(6.\times -241.8)-(3\times 0+3\times -295)\\\\\Delta H6o~rxn=-3553.4+885=-2668.4~kJ/mol$