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 side (left side of the arrow).
2. Balanced Reaction Requirement: The number of each type of atom must be equal on both sides of the equation.

• For the first option: $\ce{N_{2}(g) + O_{2}(g) + heat -> 2NO(g)}$
• Nitrogen Atoms: Left side has 2 (from $\ce{N_{2}}$), right side has $2\times1 = 2$ (from $2\ce{NO}$).
• Oxygen Atoms: Left side has 2 (from $\ce{O_{2}}$), right side has $2\times1 = 2$ (from $2\ce{NO}$).
• Heat is on the reactant side (endothermic), and the equation is balanced.
• For the second option: $\ce{N_{2}(g) + O_{2}(g) + heat -> 2N(g)}$: Right side has no oxygen atoms, so it's unbalanced.
• For the third option: $\ce{N_{2}(g) + O_{2}(g) -> 2NO(g)}$: This is a balanced reaction but does not show heat absorption (no heat on reactant side), so it's not endothermic.
• For the fourth option: $\ce{N_{2}(g) + O_{2}(g) - heat -> 2NO(g)}$: Subtracting heat means it releases heat (exothermic), not endothermic.

Answer:

A. $\ce{N_{2}(g) + O_{2}(g) + heat -> 2NO(g)}$