The problem ask on which of the following reactions and subsequent values and the value is given on you question. Base on your data and also to my formulation, solution and further simplification about the problem and the given values, i came up with an answer of ∆Hrxn = 5∆Hf(O2(g)) + 2∆Hf(C2H2(g)) - 2∆Hf(H2O(g)) - 4∆Hf(CO2(g)).