Question

1. choose the best answer.

which pair of reactants would complete this balanced chemical equation for the synthesis of nitrogen dioxide?
_ + _ → 2no₂
○ no + o₂
○ 2no + o₂
○ 2no + 2o₂
○ 4no + 2o₂

Explanation:

To balance the chemical equation for the synthesis of nitrogen dioxide ($\ce{2NO_{2}}$), we analyze the number of atoms on each side. The product has 2 N atoms and 4 O atoms (since each $\ce{NO_{2}}$ has 1 N and 2 O, and there are 2 molecules). For the reactants:

• Option 1: $\ce{NO + O_{2}}$: 1 N, 3 O (unbalanced).
• Option 2: $\ce{2NO + O_{2}}$: 2 N (from 2 $\ce{NO}$) and 2 + 2 = 4 O (2 from 2 $\ce{NO}$, 2 from $\ce{O_{2}}$), which matches the product's atom count.
• Option 3: $\ce{2NO + 2O_{2}}$: 2 N, 6 O (too many O).
• Option 4: $\ce{4NO + 2O_{2}}$: 4 N, 8 O (too many N and O).

So the balanced reactants are $\ce{2NO + O_{2}}$.

Answer:

B. $2\ce{NO} + \ce{O_{2}}$