Stoichiometric amounts of nitrogen gas and hydrogen gas react in a calorimeter to produce 5.00 g of ammonia gas. the calorimeter temperature rises 0.42°c. the calorimeter and water have a combined heat capacity of 32.16 kj/k. calculate the heat of formation of ammonia, δhf°, in kj/mol. the formation reaction for ammonia is: 0.5n2 (g) 1.5h2 (g) → nh3 (g)

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Chemistry

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8 December, 04:11

Stoichiometric amounts of nitrogen gas and hydrogen gas react in a calorimeter to produce 5.00 g of ammonia gas. the calorimeter temperature rises 0.42°c. the calorimeter and water have a combined heat capacity of 32.16 kj/k. calculate the heat of formation of ammonia, δhf°, in kj/mol. the formation reaction for ammonia is: 0.5n2 (g) 1.5h2 (g) → nh3 (g)

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Troy Finley · Answer 1

First, we determine the energy released by the reaction using the heat capacity and change in temperature as such:

Q = cΔT

Q = 32.16 * 0.42

Q = 13.51 kJ

Next, we determine the moles of ammonia formed as the heat of formation is expressed in "per mole".

Moles = mass / molecular weight

Moles = 5/17

Moles = 0.294

Heat of formation = 13.51 / 0.294

The heat of formation of ammonia is 45.95 kJ/mol