Thermochemistry, Electrochemistry, and Nuclear Chemistry PDF

## **THERMOCHEMISTRY, ELECTROCHEMISTRY AND NUCLEAR CHEMISTRY** **1. Identify the following** | Reaction | Element reduced | Element oxidized | Oxidizing agent | Reducing agent | |---|---|---|---|---| | 2Na₂SO₃ + O₂ → 2Na₂SO₄ | S | O | O<sub>2<...

## **THERMOCHEMISTRY, ELECTROCHEMISTRY AND NUCLEAR CHEMISTRY** **1. Identify the following** | Reaction | Element reduced | Element oxidized | Oxidizing agent | Reducing agent | |---|---|---|---|---| | 2Na₂SO₃ + O₂ → 2Na₂SO₄ | S | O | O₂ | Na₂SO₃ | | 2FeCl₃ + H₂S→ 3FeCl₂ + 2HCl + S | Fe | S | FeCl₃ | H₂S | | 3Mg + N₂ → Mg₃N₂ | N | Mg | N₂ | Mg | | 2AgNO₃ + Cu → Cu(NO₃)₂ + 2Ag | Ag | Cu | AgNO₃ | Cu | **II. Balance the following redox reaction** **1. MnO₄^- + I^- → Mn²⁺ + I₂ (acidic)** * 2 * [MnO₄^- + 8H⁺ + 5e^- → Mn²⁺ + 4H₂O] * 5 * [2I^- → I₂ + 2e^-] * 2MnO₄^- + 16H⁺ + 10I^- → 2Mn²⁺ + 8H₂O + 5I₂ **2. Cu²⁺ + SO ₃^2- → SO₄^2- (acidic)** * 2 * [Cu²⁺ + 2e^- → Cu] * 3 * [H₂O + SO₃^2- → SO₄^2- + 2H⁺ + 2e^-] * 2Cu²⁺ + 3H₂O + 3SO₃^2- → 2Cu + 3SO₄^2- + 6H⁺ **3. P₄ + OH^- → H₂PO₂^- (basic)** * 12e^- + 12H⁺ + P₄ → 4PH₃ * 3 * [8H₂O + 8e^- + H₂PO₂^- → PH₃ + 8OH^-] * 24H₂O + 3P₄ → 12H₂PO₂^- + 24H⁺ + 12e^- * 12OH^- + 24H₂O + 4P₄ → 4PH₃ + 12H₂PO₂^- + 12H⁺ + 12OH^- * 12OH^- + 12H₂O + 4P₄ → 4PH₃ + 12H₂PO₂^- **III. Complete the following equations** 1. Alpha decay of ²³⁸₉₂U → ²³⁴₉₀Th + ⁴₂He 2. Alpha decay of ²³⁰₉₀Th → ²²⁶₈₈Ra + ⁴₂He 3. Beta decay of ²³⁴₉₀Th → ²³⁴₉₁Pa + ⁰_-1β 4. Beta decay of ²³⁴₉₁Pa → ²³⁴₉₂U + ⁰_-1β 5. Np-237 produces an alpha particle → ²³³₉₁Pa + ⁴₂He **IV. Half-life and binding energy** **1. An isotope of cesium (ceslum-137) has a half-life of 30 years. If 1.0 g of cesium-137 disintegrates over a period of 90 years, how many grams of cesium-137 would remain?** * Given: t_1/2 = 30 years * Required: t = 90 years * Solution: * k = ln2 / t_1/2 = 0.0231 * N = N₀e^-kt * N = (1)e^-0.0231(90) * N = e^-2.07944 = 0.125 g **2. Actinium-226 has a half-life of 29 hours. If 100 mg of actinium-226 disintegrates over a period of 58 hours, how many mg of actinium-226 will remain?** * Given: t_1/2 = 29 hours * t = 58 hours * Required: N * Solution: * N = 100 (1/2)² = 25 mg **Over the dissolving of CaCl₂(s)** * CaCl₂(s) → Ca²⁺(aq) + 2Cl^-(aq) * The ΔG of CaCl₂(s) = -748.1 kJ/mol, * The ΔH of CaCl₂ = -795.8 kJ * The ΔS° of Ca²⁺ = -53.1 J/Kmol, * The ΔS° of CaCl₂ = 104.6 J/Kmol, * ΔS° = 56.5 Calculate the temperature of this reaction. * ΔG° = ΔH - TΔS * T = ΔH - ΔG / ΔS = -34.539 K **12. The production of iron and carbon dioxide from iron(III) oxide and carbon monoxide is an exothermic reaction. How many kilojoules of heat are produced when 3.40 mol Fe₂O₃ reacts with an excess of CO?** * Fe₂O₃ + 3CO → 2Fe + 3CO₂ + 26.3 KJ * (3.40 mol Fe₂O₃) (26.3 KJ/mol Fe₂O₃) = 89.42 KJ