Question

metal oxidation reaction
lithium li(s) —→ li⁺(aq) + e⁻
potassium k(s) —→ k⁺(aq) + e⁻
barium ba(s) —→ ba²⁺(aq) + 2e⁻
calcium ca(s) —→ ca²⁺(aq) + 2e⁻
sodium na(s) —→ na⁺(aq) + e⁻
magnesium mg(s) —→ mg²⁺(aq) + 2e⁻
aluminum al(s) —→ al³⁺(aq) + 3e⁻
manganese mn(s) —→ mn²⁺(aq) + 2e⁻
zinc zn(s) —→ zn²⁺(aq) + 2e⁻
chromium cr(s) —→ cr³⁺(aq) + 3e⁻
iron fe(s) —→ fe²⁺(aq) + 2e⁻
cobalt co(s) —→ co²⁺(aq) + 2e⁻
nickel ni(s) —→ ni²⁺(aq) + 2e⁻
tin sn(s) —→ sn²⁺(aq) + 2e⁻
lead pb(s) —→ pb²⁺(aq) + 2e⁻
hydrogen h₂(g) —→ 2 h⁺(aq) + 2e⁻
copper cu(s) —→ cu²⁺(aq) + 2e⁻
silver ag(s) —→ ag⁺(aq) + e⁻
mercury hg(l) —→ hg²⁺(aq) + 2e⁻
platinum pt(s) —→ pt²⁻(aq) + 2e⁻
gold au(s) —→ au³⁺(aq) + 3e⁻
copyright © 2009 pearson prentice hall, inc.
question 1
select all the reactant combinations that will react spontaneously.
☐ zn and cuso₄
☐ al and hgcl₂
☐ lead and hydrobromic acid
☐ silver and nitric acid

Explanation:

Step1: Recall Spontaneity Rule

A redox reaction is spontaneous if the reducing agent (metal) is more easily oxidized (higher on the list) than the oxidizing agent's metal (in its compound).

Step2: Analyze Zn and CuSO₄

- Zn's oxidation: \( \text{Zn}(s) ightarrow \text{Zn}^{2+}(aq) + 2e^- \)
- Cu²⁺ (from CuSO₄) reduction: \( \text{Cu}^{2+}(aq) + 2e^- ightarrow \text{Cu}(s) \)
- Zn is higher (more easily oxidized) than Cu. So reaction is spontaneous.

Step3: Analyze Al and HgCl₂

- Al's oxidation: \( \text{Al}(s) ightarrow \text{Al}^{3+}(aq) + 3e^- \)
- Hg²⁺ (from HgCl₂) reduction: \( \text{Hg}^{2+}(aq) + 2e^- ightarrow \text{Hg}(l) \)
- Al is higher (more easily oxidized) than Hg. So reaction is spontaneous.

Step4: Analyze Lead and Hydrobromic Acid

- Pb's oxidation: \( \text{Pb}(s) ightarrow \text{Pb}^{2+}(aq) + 2e^- \)
- H⁺ (from HBr) reduction: \( 2\text{H}^+(aq) + 2e^- ightarrow \text{H}_2(g) \)
- Pb is higher (more easily oxidized) than H. So reaction is spontaneous.

Step5: Analyze Silver and Nitric Acid

- Ag's oxidation: \( \text{Ag}(s) ightarrow \text{Ag}^+(aq) + e^- \)
- H⁺ (from HNO₃) reduction: \( 2\text{H}^+(aq) + 2e^- ightarrow \text{H}_2(g) \) (but HNO₃ is a strong oxidizing agent, but from the list, Ag is lower than H? Wait, no—wait, the list: H is at a certain position. Wait, Ag is below H? Wait, no: H is \( \text{H}_2(g) ightarrow 2\text{H}^+(aq) + 2e^- \), and Ag is \( \text{Ag}(s) ightarrow \text{Ag}^+(aq) + e^- \). Wait, the "ease of oxidation increases" upward. So H is above Ag? Wait, no: looking at the list, H is between Sn/Pb and Cu. Ag is below Cu. So H is more easily oxidized than Ag. So Ag cannot reduce H⁺ (from HNO₃, but HNO₃ is a strong oxidizer, but in standard redox, Ag is below H, so Ag + H⁺ (from HNO₃, but HNO₃'s NO₃⁻ is the oxidizing agent, not H⁺. Wait, maybe I made a mistake. Wait, nitric acid is a strong oxidizing agent, but the question is about Ag and HNO₃. But from the given list, Ag is less easily oxidized than H. So Ag + H⁺ (from HNO₃, but HNO₃'s redox is with NO₃⁻, not H⁺. But the problem's list is for metal/metal ion. So for Ag and HNO₃, if we consider the metal (Ag) and the cation (but HNO₃ has NO₃⁻, not a metal cation. Wait, maybe the question is about metal and metal salt. Wait, the options: Zn and CuSO₄ (Cu²⁺), Al and HgCl₂ (Hg²⁺), Lead and HBr (H⁺), Silver and HNO₃ (H⁺ or NO₃⁻). But from the list, Pb is above H (since H is at a position, Pb is above H: Pb is Sn, Pb, then H. So Pb is more easily oxidized than H, so Pb + HBr (H⁺) will react. Ag is below H, so Ag + H⁺ (from HNO₃, but HNO₃ is a strong oxidizer, but in the list, Ag is less easily oxidized than H, so Ag + H⁺ (from HBr-like, but HNO₃ is different). Wait, maybe the last one: Silver and nitric acid. From the list, Ag is below H, so Ag cannot oxidize H⁺, but HNO₃ is a strong oxidizer, but the problem's list is for metal/metal ion. So maybe the intended is: Ag is below H, so Ag + H⁺ (from HNO₃, but as a metal-acid reaction, Ag is below H, so no reaction. But wait, the first three: Zn > Cu, Al > Hg, Pb > H. So those three are spontaneous. Wait, but maybe I messed up Ag. Wait, let's recheck:

Wait, the "ease of oxidation increases" as we go up the list. So Li is most easily oxidized (top), Au least (bottom). So:

- Zn is above Cu (Zn is more easily oxidized than Cu) → Zn + CuSO₄: spontaneous.
- Al is above Hg (Al is more easily oxidized than Hg) → Al + HgCl₂: spontaneous.
- Pb is above H (Pb is more easily oxidized than H) → Pb + HBr: spontaneous.
- Ag is below H (Ag is less easily oxidized than H) → Ag + HNO₃: not spontaneous (since Ag can't reduce H⁺, and HNO₃'s NO₃⁻ is a different oxidant, but the problem's list is for metal/metal ion, so maybe the question considers H⁺ as the oxidant here, so Ag can't react with H⁺, so not spontaneous.

So the spontaneous ones are Zn and CuSO₄, Al and HgCl₂, Lead and hydrobromic acid.

Answer:

The reactant combinations that react spontaneously are:

• Zn and \( \text{CuSO}_4 \)
• Al and \( \text{HgCl}_2 \)
• Lead and hydrobromic acid

(So check the boxes for these three options.)