Question

1. choose the best answer. what is the balanced equation for the combustion of magnesium? \\( \text{mg}(s) + \text{o}_2(g) \

ightarrow \text{mgo}(s) \\) \\( \text{mg}(s) + 2\text{o}_2(g) \
ightarrow \text{mgo}_4^{2-}(aq) \\) \\( 2\text{mg}(s) + \text{o}_2(g) \
ightarrow 2\text{mgo}(s) \\) \\( 2\text{mg}(s) + \text{o}_2(g) \
ightarrow \text{mgo}_2(g) \\)

Explanation:

Step1: Recall Mg combustion product

Magnesium burns in oxygen to form solid magnesium oxide ($\text{MgO}(s)$), not other species like $\text{MgO}_4^{2-}$ or $\text{MgO}_2$.

Step2: Balance the chemical equation

Count Mg and O atoms:

• Unbalanced: $\text{Mg}(s) + \text{O}_2(g)

ightarrow \text{MgO}(s)$

• Balance O: Add 2 to $\text{MgO}$: $\text{Mg}(s) + \text{O}_2(g)

ightarrow 2\text{MgO}(s)$

• Balance Mg: Add 2 to $\text{Mg}$: $2\text{Mg}(s) + \text{O}_2(g)

ightarrow 2\text{MgO}(s)$

Step3: Match to options

Check states: Mg is solid, $\text{O}_2$ is gas, $\text{MgO}$ is solid.

Answer:

B. $2\text{Mg}(s) + \text{O}_2(g)
ightarrow 2\text{MgO}(s)$