Fill in the blanks with suitable verbs from the brackets. The army _____ the enemy camp at night. The river…

Question

Fill in the blanks with suitable verbs from the brackets. The army _____ the enemy camp at night. The river _____ across the town. Write the balanced cathode reaction for a lead-acid battery.

ScanSolve AI Tutor · Accepted Answer

Here are the solutions for section G and the chemistry problem.

G. Fill in the blanks with suitable verbs from the brackets.

The army attacked the enemy camp at night.
The river flowed across the town.

Chemistry Problem

The reaction at the cathode of a lead-acid battery during discharge, starting with $\text{PbO}_2$ and consuming $2e^-$ , to produce $\text{PbSO}_4$ and $\text{H}_2\text{O}$ is:

Identify the given components and the type of reaction.
The problem shows $\text{PbO}_2$ at the cathode, $2e^-$ consumed, and $\text{PbSO}_4 + 2\text{H}_2\text{O}$ as products. This is a reduction half-reaction in a lead-acid battery.
Write the unbalanced half-reaction with the given species.
$\text{PbO}_2 + 2e^- \rightarrow \text{PbSO}_4 + 2\text{H}_2\text{O}$
Balance the atoms other than oxygen and hydrogen.
Lead (Pb) is already balanced (1 on each side). Sulfur (S) is present in $\text{PbSO}_4$ on the product side, so we need $\text{SO}_4^{2-}$ on the reactant side.
$\text{PbO}_2 + \text{SO}_4^{2-} + 2e^- \rightarrow \text{PbSO}_4 + 2\text{H}_2\text{O}$
Balance oxygen atoms by adding water molecules (if needed) and hydrogen atoms by adding $\text{H}^+$ ions (since it's an acidic environment).
Reactant side has 2 oxygen from $\text{PbO}_2$ and 4 oxygen from $\text{SO}_4^{2-}$ (total 6 oxygen). Product side has 4 oxygen from $\text{PbSO}_4$ and 2 oxygen from $2\text{H}_2\text{O}$ (total 6 oxygen). Oxygen is balanced.
Product side has 4 hydrogen atoms from $2\text{H}_2\text{O}$ . Add $4\text{H}^+$ to the reactant side.
$\text{PbO}_2(s) + \text{SO}_4^{2-}(aq) + 4\text{H}^+(aq) + 2e^- \rightarrow \text{PbSO}_4(s) + 2\text{H}_2\text{O}(l)$
Verify the charge balance.
Reactant side charge: $(0) + (-2) + (+4) + (-2) = 0$
Product side charge: $(0) + (0) = 0$
The charges are balanced.

The complete balanced half-reaction is:
$\boxed{\text{PbO}_2(s) + \text{SO}_4^{2-}(aq) + 4\text{H}^+(aq) + 2e^- \rightarrow \text{PbSO}_4(s) + 2\text{H}_2\text{O}(l)}$

Fill in the blanks with suitable verbs from the brackets. The army _ the enemy camp at night. The river _ across the town. Write the balanced cathode reaction for a lead-acid battery.

Step-by-step solution

Identify the given components and the type of reaction.

Write the unbalanced half-reaction with the given species.

Balance the atoms other than oxygen and hydrogen.

Balance oxygen atoms by adding water molecules (if needed) and hydrogen atoms by adding $\text{H}^+$ ions (since it's an acidic environment).

Verify the charge balance.

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