13: Homework Solutions

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Oxidation-Reduction (Redox) Reactions

(01) \[CH_4 + 2 O_2 \rightarrow CO_2 + 2 H_2O\]

Carbon is oxidized because it lost electrons: \(C^{-4}\) to \(C^{+4}\).
\(O_2\) is reduced because it gained electrons: \(O^0\) to \(O^{2-}\).

(02)

"LEO says GER" LEO: Loss of Electrons is Oxidation and Gain of Electrons is Reduction.
"OIL RIG" Oxidation Is Loss of electrons and Reduction Is Gain of electrons

(03)

oxidation
oxidation
reduction
reduction

(04) For the following equations, find the oxidation and reduction numbers of each element to determine which compound is oxidized and which is reduced and label them as such. Write the oxidation ½-reaction and the reduction ½-reaction.

a. oxidation half-reaction: \(Al^0 \rightarrow Al^{3+} + 3 e^-\)

reduction half-reaction: \(3 K^+ + 3 e^- \rightarrow 3K^0\) which simplifies toK⁺ + e^- → K⁰

b. oxidation half-reaction: \(2 H_2^0 \rightarrow 4 H^+ + 4 e^-\) which simplifies to H₂⁰ → 2 H⁺ + 2 e^-

reduction half-reaction: \(O_2^0 + 4 e^- \rightarrow 2 O^{2-}\)

c. oxidation half-reaction: \(2 C^{2-} \rightarrow 2 C^{4+} + 12 e^-\) which simplifies to C²^- → C⁴⁺ + 6 e^-

reduction half-reaction: \(3 O_2^0 + 12 e^- \rightarrow 6 O^{2-}\) which simplifies toO₂⁰ + 4 e^- → 2 O^2-

d. oxidation half-reaction: \(3 H_2^0 \rightarrow 6 H^+ + 6 e^-\) which simplifies to H₂⁰ → 2 H⁺ + 2 e^-

reduction half-reaction: \(N_2^0 + 6 e^- \rightarrow 2 N^{3-}\)

e. oxidation half-reaction: \(Cu^0 \rightarrow Cu^{2+} + 2 e^-\)

reduction half-reaction: \(2 H^+ + 2 e^- \rightarrow H_2^0 \)

(05) Determine whether each compound below has undergone oxidation or reduction.

oxidation
reduction
reduction
neither (hydration)
reduction

(06)

reducing agent
oxidizing agent
oxidizing agent
reducing agent

(07)

ch13q7answers abc.png

d. no oxidation because there are no hydrogen atoms to lose

e. no oxidation because there are no hydrogen atoms to lose

(08) For each of the following organic structures, show what the product would look like after a reduction. If a reaction cannot take place, explain why.