AP Chemistry 4.9: Redox Half-Reactions

Practice AP Chemistry questions on writing oxidation half-reactions and combining half-reactions into balanced net ionic redox equations with conserved atoms and charge.

Exam points

Explain how reaction rates depend on collision frequency, activation energy and molecular orientation.
Apply rate laws, catalysts and concentration data to predict changes in reaction speed.

[Maximum number: 2]

A scientist constructs a galvanic cell as shown in the diagram. As the cell operates, the $\mathrm{Zn}(s)$

electrode increases in mass and the $\mathrm{Al}(s)$ electrode decreases in mass. A data table with the

standard reduction potentials for the substances follows the diagram.

Figure for Question 4.9.A—Represent a balanced redox reaction equation using half-reactions question 1 — AP Chemistry

Table for Question 4.9.A—Represent a balanced redox reaction equation using half-reactions question 1 — AP Chemistry

(a)

Write the half-reaction for the oxidation that occurs at the anode.

[ 1 ]

A For the correct equation (state symbols not required):

Point 01

$\mathrm{Al}(s) \rightarrow \mathrm{Al}^{3+}(a q)+3 e^{-}$

(b)

Write the balanced net ionic equation for the overall reaction that occurs in the galvanic cell.

[ 1 ]

B For the correct balanced net ionic equation (state symbols not required):

Point 02

$2 \mathrm{Al}(s)+3 \mathrm{Zn}^{2+}(a q) \rightarrow 2 \mathrm{Al}^{3+}(a q)+3 \mathrm{Zn}(s)$

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4.9.A—Represent a balanced redox reaction equation using half-reactions question 1

Question (a)

Question (b)