Question

this equation represents a balanced chemical reaction: fe(s) + cuso₄(aq) → feso₄(aq) + cu(s)
which type of chemical reaction is represented?

• double replacement
• decomposition
• single replacement
• synthesis

this is a chemical equation to represent a reaction: hgo → hg + o₂
which of these substances is/are reactants in this chemical reaction?

• hgo
• hg
• o₂
• hg and o₂

balance the equation:
fe + o₂ → __ fe₂o₃

• 2fe + o₂ → fe₂o₃
• 4fe + 3o₂ → 2fe₂o₃
• 3fe + o₂ → fe₃o₂
• 2fe + 3o₂ → fe₂o₃

Explanation:

First Question (Chemical Reaction Type)

To determine the reaction type, analyze the equation \( \text{Fe}(s) + \text{CuSO}_4(aq)
ightarrow \text{FeSO}_4(aq) + \text{Cu}(s) \). In a single - replacement reaction, one element replaces another in a compound. Here, iron (Fe) replaces copper (Cu) in copper sulfate (\( \text{CuSO}_4 \)). Double - replacement involves two compounds exchanging ions, decomposition is a single compound breaking down, and synthesis is combining substances. So this is a single - replacement reaction.

In a chemical equation, reactants are on the left side of the arrow. For the equation \( \text{HgO}
ightarrow \text{Hg} + \text{O}_2 \), \( \text{HgO} \) is on the left, so it is the reactant. \( \text{Hg} \) and \( \text{O}_2 \) are products (on the right).

Step 1: Count atoms on each side

• For Fe: Left side has 1 Fe atom, right side (in \( \text{Fe}_2\text{O}_3 \)) has 2 Fe atoms.
• For O: Left side (in \( \text{O}_2 \)) has 2 O atoms, right side (in \( \text{Fe}_2\text{O}_3 \)) has 3 O atoms.

Step 2: Balance Fe first

To balance Fe, put a coefficient of 2 in front of \( \text{Fe}_2\text{O}_3 \) (but let's use the trial - and - error with the given options). Let's check the option \( 4\text{Fe}+3\text{O}_2
ightarrow2\text{Fe}_2\text{O}_3 \):

• Fe: Left - 4, Right - \( 2\times2 = 4 \) (balanced).
• O: Left - \( 3\times2=6 \), Right - \( 2\times3 = 6 \) (balanced).

Other options:

• \( 2\text{Fe}+\text{O}_2

ightarrow\text{Fe}_2\text{O}_3 \): O atoms - left 2, right 3 (not balanced).

• \( 3\text{Fe}+\text{O}_2

ightarrow\text{Fe}_3\text{O}_2 \): Incorrect formula for the product.

• \( 2\text{Fe}+3\text{O}_2

ightarrow\text{Fe}_2\text{O}_3 \): O atoms - left 6, right 3 (not balanced).

Answer:

C. Single Replacement

Second Question (Reactants in \( \text{HgO}

ightarrow \text{Hg} + \text{O}_2 \))