Question

which type of reaction occurs in the following?
2hgo(s) → 2hg(l) + o₂(g)
○ a decomposition reaction in which a metal is reduced
○ an acid-base neutralization reaction to produce oxygen gas
○ a displacement reaction involving two metals
○ a combustion reaction including burning a metal in oxygen

Explanation:

1. Analyze the reaction \(2\text{HgO}(s)

ightarrow2\text{Hg}(l) + \text{O}_2(g)\): A single reactant (\(\text{HgO}\)) breaks down into two products (\(\text{Hg}\) and \(\text{O}_2\)), so it is a decomposition reaction.

1. For the oxidation - reduction aspect: In \(\text{HgO}\), the oxidation state of \(\text{Hg}\) is \( + 2\), and in \(\text{Hg}(l)\), the oxidation state of \(\text{Hg}\) is \(0\). A decrease in oxidation state means reduction. So \(\text{Hg}\) (a metal) is reduced.
2. Eliminate other options:

• An acid - base neutralization reaction involves an acid and a base reacting to form a salt and water. There are no acids or bases in this reaction, so the second option is incorrect.
• A displacement reaction involves one element displacing another in a compound. This reaction has only one reactant, so it is not a displacement reaction, and the third option is incorrect.
• A combustion reaction usually involves a substance reacting with oxygen to form oxides. Here, \(\text{HgO}\) is decomposing, not a metal burning in oxygen (the reverse of what is happening here), so the fourth option is incorrect.

Answer:

a decomposition reaction in which a metal is reduced