Specify which of the following equations represent oxidationreduction reactions, and indicate the oxidizing agent, the reducing agent, the species being oxidized, and the species being reduced. a. \(\mathrm{CH}_{4}(g)+\mathrm{H}_{2} \mathrm{O}(g) \rightarrow \mathrm{CO}(g)+3 \mathrm{H}_{2}(g)\) b. \(2 \mathrm{AgNO}_{3}(a q)+\mathrm{Cu}(s) \rightarrow \mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}(a q)+2 \mathrm{Ag}(s)\) c. \(\mathrm{Zn}(s)+2 \mathrm{HCl}(a q) \rightarrow \mathrm{ZnCl}_{2}(a q)+\mathrm{H}_{2}(g)\) d. \(2 \mathrm{H}^{+}(a q)+2 \mathrm{CrO}_{4}^{2-}(a q) \rightarrow \mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}(a q)+\mathrm{H}_{2} \mathrm{O}(i)\)

For each equation, we will analyze the elements' oxidation states in the reactants and products. a. CH\(_4\) + H\(_2\)O → CO + 3H\(_2\) In CH\(_4\), C has -4, H has +1 In H\(_2\)O, O has -2, H has +1 In CO; C has +2, O has -2 In H\(_2\), H has +1 b. 2AgNO\(_3\) + Cu → Cu(NO\(_3\))\(_2\) + 2Ag In AgNO\(_3\), Ag has +1, N has +5, O has -2 In Cu, Cu has 0 In Cu(NO\(_3\))\(_2\), Cu has +2, N has +5, O has -2 In Ag, Ag has 0 c. Zn + 2HCl → ZnCl\(_2\) + H\(_2\) In Zn, Zn has 0 In HCl, H has +1, Cl has -1 In ZnCl\(_2\), Zn has +2, Cl has -1 In H\(_2\), H has +1 d. 2H\(^+\)(aq) + 2CrO\(_4^{2-}\)(aq) → Cr\(_2\)O\(_7^{2-}\)(aq) + H\(_2\)O(l) In H\(^+\), H has +1 In CrO\(_4^{2-}\), Cr has +6, O has -2 In Cr\(_2\)O\(_7^{2-}\), Cr has +6, O has -2 In H\(_2\)O, H has +1, O has -2

Now, we examine the oxidation states to see if any changed during the reaction. a. C: -4 to +2 (change), other elements' oxidation states remain the same. Redox reaction. b. Ag: +1 to 0 (change), Cu: 0 to +2 (change), other elements' oxidation states remain the same. Redox reaction. c. Zn: 0 to +2 (change), H: +1 to 0 (change). Redox reaction. d. The oxidation states of the elements remain the same. Not a redox reaction.

Now we identify the oxidizing agents, reducing agents, and the species being oxidized and reduced for the redox reactions (a, b, and c). a. Oxidizing Agent: H\(_2\)O Reducing Agent: CH\(_4\) Species oxidized: C in CH\(_4\) Species reduced: O in H\(_2\)O b. Oxidizing Agent: AgNO\(_3\) Reducing Agent: Cu Species oxidized: Cu Species reduced: Ag in AgNO\(_3\) c. Oxidizing Agent: HCl Reducing Agent: Zn Species oxidized: Zn Species reduced: H in HCl