Question

which reaction is an example of a balanced endothermic reaction? answer options: select one of four n₂ (g) + o₂ (g) + heat → 2no (g) n₂ (g) + o₂ (g) + heat → 2n (g) n₂ (g) + o₂ (g) → 2no (g) n₂ (g) + o₂ (g) - heat → 2no (g)

Explanation:

1. Endothermic Reaction Requirement: An endothermic reaction absorbs heat, so heat should be on the reactant (left) side (form: reactants + heat → products).
2. Balanced Equation Requirement: The number of each atom on the reactant side must equal the number on the product side.

• Option 1 ($\boldsymbol{\ce{N2(g) + O2(g) + heat → 2NO(g)}}$):
• Reactants: 2 N (from $\ce{N2}$), 2 O (from $\ce{O2}$), heat absorbed.
• Products: 2 N (from $2\ce{NO}$), 2 O (from $2\ce{NO}$). Atoms are balanced. Heat is on the reactant side (endothermic).
• Option 2 ($\boldsymbol{\ce{N2(g) + O2(g) + heat → 2N(g)}}$): Products have only N atoms (no O), so O atoms are unbalanced. Eliminate.
• Option 3 ($\boldsymbol{\ce{N2(g) + O2(g) → 2NO(g)}}$): No heat term, so it is not endothermic (could be exothermic or just a reaction without heat labeled). Eliminate.
• Option 4 ($\boldsymbol{\ce{N2(g) + O2(g) - heat → 2NO(g)}}$): Subtracting heat means heat is released (exothermic), which contradicts "endothermic". Eliminate.

Answer:

A. $\ce{N2(g) + O2(g) + heat → 2NO(g)}$