Thermochemical Equations

A thermochemical equation is a stoichiometric question that now involves the variable of ΔHReaction. Instead of doing a mole to mole comparison we will now do a mole to ΔH comparison. 

Enthalpy and Chemical Reactions

Concept: Understanding Thermochemical Equations


Example: Iron is reacts with oxygen according to the following equation at around 2000oC.  (0:35 – 4:10)

4 Fe (s)  +  3 O­2 (g)  → 2 Fe2O3 (s)         

ΔHo = + 65.2 kJ/mol

Calculate the amount of grams of iron (III) oxide, Fe2O3, produced from the absorption of 4.82 x 109 J. 


Problem: Nitromethane (CH3NO2), sometimes used as a fuel for drag racing, burns according to the following reaction: 4 CH3NO2 (l) + 7 O2 (g) -----> 4 CO2 (g) + 6 H2O (g) + 4 NO2 (g) ?H = ? 2441.6 kJ How much heat is released by burning 125.0 g of nitromethane (MW: 61.044 g/mol)?