Q1. (a) +7; (b) +2; (c) −3.
Q2. Galvanic = spontaneous, E°cell > 0, generates electricity. Electrolytic = non-spontaneous, requires external V, E°cell < 0.
Q3. Ag⁺/Ag (right side = cathode).
Q4. E°cell = 0.80 − 0.34 = +0.46 V. Cu + 2Ag⁺ → Cu²⁺ + 2Ag.
Q5. Cr₂O₇²⁻ + 14H⁺ + 6I⁻ → 2Cr³⁺ + 3I₂ + 7H₂O.
Q6. Q = 0.500 × 3600 = 1800 C → n(e⁻) = 1800/96485 = 0.01866 mol; n(Ag) = 0.01866 mol → m = 2.01 g.
Q7. MnO₄⁻ + 8H⁺ + 5Fe²⁺ → Mn²⁺ + 5Fe³⁺ + 4H₂O. n(MnO₄⁻) = 0.0200 × 0.02250 = 4.50×10⁻⁴ mol → n(Fe²⁺) = 5 × 4.50×10⁻⁴ = 2.25×10⁻³ mol → [Fe²⁺] = 2.25×10⁻³/0.02500 = 0.0900 M.
Q8. Diagram should show Zn(s)|ZnSO₄ on left (anode, oxidation, e⁻ leave); Cu(s)|CuSO₄ on right (cathode, reduction, e⁻ enter); salt bridge with NO₃⁻/Na⁺ migrating to balance charge.
Q9. Salt bridge completes the circuit by allowing ions (cations to cathode, anions to anode) to migrate, preventing charge buildup that would halt e⁻ flow.
Q10. Mg/Zn has more negative E° than Fe → preferentially oxidized; supplies e⁻ to Fe, keeping Fe in reduced (un-corroded) state.
Q11. n(Al) = 1000/26.98 = 37.06 mol → n(e⁻) = 111.2 mol → Q = 111.2 × 96485 = 1.073×10⁷ C. E = QV = 1.073×10⁷ × 5.00 = 5.36×10⁷ J ≈ 14.9 kWh/kg Al.
Q12. Anode: Pb + SO₄²⁻ → PbSO₄ + 2e⁻. Cathode: PbO₂ + SO₄²⁻ + 4H⁺ + 2e⁻ → PbSO₄ + 2H₂O. SO₄²⁻ consumed → H₂SO₄ concentration (and density) drops.
Q13. Primary: Zn-C dry cell — landfill heavy metals. Secondary: Li-ion — mining + recycling. Fuel cell: H₂ — H₂ production source/footprint.