Oxidizing and reducing agents Knowledge-Based Practice

Questions

1. 1.

   In the redox reaction $\text{Cr}_2\text{O}_7^{2-}(aq) + 6\text{Fe}^{2+}(aq) + 14\text{H}^+(aq) \rightarrow 2\text{Cr}^{3+}(aq) + 6\text{Fe}^{3+}(aq) + 7\text{H}_2\text{O}(l)$, which species acts as the oxidizing agent, and how does the oxidation number of its key atom change?

   • A) $\text{Fe}^{2+}$, because the oxidation number of iron increases from +2 to +3.
   • B) $\text{Fe}^{2+}$, because the oxidation number of iron decreases from +3 to +2.
   • C) $\text{Cr}_2\text{O}_7^{2-}$, because the oxidation number of chromium decreases from +6 to +3.
   • D) $\text{Cr}_2\text{O}_7^{2-}$, because the oxidation number of chromium increases from +3 to +6.
2. 2.

   In the chemical reaction represented by the equation $\text{PbO}(s) + \text{CO}(g) \rightarrow \text{Pb}(s) + \text{CO}_2(g)$, which substance acts as the reducing agent, and why?

   • A) $\text{PbO}$, because lead increases its oxidation state from $0$ to $+2$.
   • B) $\text{CO}_2$, because carbon decreases its oxidation state from $+4$ to $+2$.
   • C) $\text{PbO}$, because lead decreases its oxidation state from $+2$ to $0$.
   • D) $\text{CO}$, because carbon increases its oxidation state from $+2$ to $+4$.
3. 3.

   Consider the balanced redox reaction: $2\text{Fe}^{3+}(aq) + 2\text{I}^-(aq) \rightarrow 2\text{Fe}^{2+}(aq) + \text{I}_2(s)$ Which pair correctly identifies the reducing agent and the substance reduced?

   • A) Reducing agent: $\text{Fe}^{3+}$; substance reduced: $\text{I}^-$
   • B) Reducing agent: $\text{I}^-$; substance reduced: $\text{Fe}^{3+}$
   • C) Reducing agent: $\text{I}_2$; substance reduced: $\text{Fe}^{2+}$
   • D) Reducing agent: $\text{Fe}^{3+}$; substance reduced: $\text{Fe}^{2+}$
4. 4.

   In the redox reaction represented by the equation $\text{MnO}_2(s) + 4\text{HCl}(aq) \rightarrow \text{MnCl}_2(aq) + \text{Cl}_2(g) + 2\text{H}_2\text{O}(l)$, which reactant acts as the oxidizing agent, and why?

   • A) $\text{MnO}_2$, because manganese decreases in oxidation number from +4 to +2 by gaining electrons.
   • B) $\text{HCl}$, because chlorine increases in oxidation number from -1 to 0 by losing electrons.
   • C) $\text{HCl}$, because hydrogen decreases in oxidation number by accepting electrons from chlorine.
   • D) $\text{MnO}_2$, because oxygen increases in oxidation number by donating electrons to hydrogen.
5. 5.

   In the redox reaction represented by the equation $\text{Cu}(s) + 2\text{Ag}^+(aq) \rightarrow \text{Cu}^{2+}(aq) + 2\text{Ag}(s)$, which species acts as the reducing agent, and what is the reason?

   • A) $\text{Ag}^+(aq)$, because it loses electrons and causes oxidation.
   • B) $\text{Cu}(s)$, because it gains electrons and causes reduction.
   • C) $\text{Cu}(s)$, because it loses electrons and causes $\text{Ag}^+(aq)$ to be reduced.
   • D) $\text{Ag}^+(aq)$, because it gains electrons and is oxidized in the process.

Answers and step-by-step solutions appear after you finish the test.