Question

Suppose that stoichiometric amounts of nitrogen gas and hydrogen gas react in a calorimeter to produce 5.00 g of ammonia gas. The calorimeter temperature rises 0.42ÁC. The calorimeter and water have a combined heat capacity of 32.16 kJ/K. Calculate the heat of formation of ammonia, _HÁf, in kJ/mol. The formation reaction for ammonia is: 0.5N2(g) + 1.5H2(g) _ NH3(g).

Answer 1

0.42 C * 32.14kj/1 = 13.499 KJ . . .rounded to 13.5

5g NH3 * 1 mol NH3/17 g NH3 = 0.294 mol NH3

kJ/mol = 13.5 kJ/0.294 = 45.9 kJ/Mol

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