^^ multiplied the reaction to 2, and flipped it (what happens to the reaction also happens to the ▵Hf.
6H₂ + 3O₂ → 6H₂O ▵Hf = -1716 kJ/mol
^^ multiplied reaction to 6 to get 3O₂, then flipped the reaction
4NH₃ + 3O₂ → 2N₂ + 6H₂O ▵Hrxn = -1532 kJ/mol
^^ add the reactions. 6H₂ was cancelled because both sides of the reactions have 6H₂
I know this problem was posted a month ago, but I just wanted to post this in case anyone still needs it. Sorry if you don't understand my explanation (it's very hard to explain ><). I'm not even sure if my answer is correct.
Answers & Comments
Answer:
▵Hrxn = -1532 kJ/mol
Explanation:
4NH₃ → 2N₂ + 6H₂ ▵Hf = 184 kJ/mol
6H₂ + 3O₂ → 6H₂O ▵Hf = -1716 kJ/mol
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4NH₃ + 3O₂ → 2N₂ + 6H₂O ▵Hrxn = -1532 kJ/mol
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4NH₃ → 2N₂ + 6H₂ ▵Hf = 184 kJ/mol
^^ multiplied the reaction to 2, and flipped it (what happens to the reaction also happens to the ▵Hf.
6H₂ + 3O₂ → 6H₂O ▵Hf = -1716 kJ/mol
^^ multiplied reaction to 6 to get 3O₂, then flipped the reaction
4NH₃ + 3O₂ → 2N₂ + 6H₂O ▵Hrxn = -1532 kJ/mol
^^ add the reactions. 6H₂ was cancelled because both sides of the reactions have 6H₂
I know this problem was posted a month ago, but I just wanted to post this in case anyone still needs it. Sorry if you don't understand my explanation (it's very hard to explain ><). I'm not even sure if my answer is correct.