Question

which of the following reactions are redox reactions? check all that apply. view available hint(s) 4li(s) + o₂(g) → 2li₂o(s) zn(s) + cu²⁺(aq) → zn²⁺(aq) + cu(s) pb(no₃)₂(aq) + na₂so₄(aq) → pbso₄(s) + 2nano₃(aq) hbr(aq) + koh(aq) → h₂o(l) + kbr(aq)

Explanation:

Step1: Analyze the first reaction

In \(4Li(s)+O_{2}(g)\to2Li_{2}O(s)\), for \(Li\): \(Li\) in \(Li(s)\) has an oxidation state of \(0\), and in \(Li_{2}O\) it is \(+ 1\). For \(O\): \(O\) in \(O_{2}(g)\) has an oxidation state of \(0\), and in \(Li_{2}O\) it is \(-2\). There are changes in oxidation states.

Step2: Analyze the second reaction

In \(Zn(s)+Cu^{2 +}(aq)\to Zn^{2 +}(aq)+Cu(s)\), \(Zn\) in \(Zn(s)\) has an oxidation state of \(0\), and in \(Zn^{2+}(aq)\) it is \(+2\). \(Cu\) in \(Cu^{2+}(aq)\) has an oxidation state of \(+2\), and in \(Cu(s)\) it is \(0\). There are changes in oxidation states.

Step3: Analyze the third reaction

In \(Pb(NO_{3})_{2}(aq)+Na_{2}SO_{4}(aq)\to PbSO_{4}(s)+2NaNO_{3}(aq)\), it is a double - displacement reaction. The oxidation states of \(Pb\), \(N\), \(O\), \(Na\), \(S\) remain the same throughout the reaction.

Step4: Analyze the fourth reaction

In \(HBr(aq)+KOH(aq)\to H_{2}O(l)+KBr(aq)\), it is an acid - base neutralization reaction (double - displacement). The oxidation states of \(H\), \(Br\), \(K\), \(O\) remain the same throughout the reaction.

Answer:

\(4Li(s)+O_{2}(g)\to2Li_{2}O(s)\), \(Zn(s)+Cu^{2 +}(aq)\to Zn^{2 +}(aq)+Cu(s)\)