Question

Consider the following reaction. 2Fe2O3 --> 4Fe + 3O2 deltaH = +824.2KJ The formation of 42.0 g of O2 results in? 1) the absorption of 361 kJ of heat. 2) the absorption of 11500 kJ of heat. 3) the absorption of 1080 kJ of heat.

Answer 1

molar mass of O = 16g

16 . 2. 3 = 96

=>

96g of O2 results in +824.2KJ

so,

42 g of O2 results in ?

Answer 2

First convert g of O2 to moles. Then use the conversion of 824.2kJ /3 moles (per the equation) to determine how many kJ/mole. Divide by the number of moles you have (converted from g of O2) and you have your answer.