Which direction, forwards or reverse, is exothermic for N2 + 3H2 ⇌ 2NH3 ΔH = -92 kJmol-1?

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Study for the IGCSE Edexcel Chemistry exam. Prepare with multiple choice questions and detailed explanations. Get ready to succeed on your test!

Multiple Choice

Which direction, forwards or reverse, is exothermic for N2 + 3H2 ⇌ 2NH3 ΔH = -92 kJmol-1?

Explanation:
When a reaction has a negative enthalpy change, it releases heat. Here, the forward direction N2 + 3H2 → 2 NH3 has ΔH = -92 kJ/mol, so it is exothermic—the forward path releases heat. The reverse direction would require energy input (+92 kJ/mol), so it’s endothermic. Therefore, the exothermic direction is the forward one. Choices stating both or neither would conflict with the single enthalpy sign provided for the written direction.

When a reaction has a negative enthalpy change, it releases heat. Here, the forward direction N2 + 3H2 → 2 NH3 has ΔH = -92 kJ/mol, so it is exothermic—the forward path releases heat. The reverse direction would require energy input (+92 kJ/mol), so it’s endothermic. Therefore, the exothermic direction is the forward one. Choices stating both or neither would conflict with the single enthalpy sign provided for the written direction.

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