CHEM 104 Module 3 – Portage Learning Exam (Solubility, Entropy, Gibbs Free Energy)

This document is a module exam for Portage Learning CHEM 104 (Module 3) covering solubility product (Ksp), entropy (ΔS), Gibbs free energy (ΔG), and spontaneity. Questions include calculation of molar solubility of BaF₂ (Ksp = 1.0 × 10⁻⁶ → s = 6.3 × 10⁻³ mol/L), calculation of Ksp of MnS from solubility (0.0001375 g/100 mL → Ksp = 2.496 × 10⁻¹⁰), precipitation prediction for PbI₂ (mixing 1.0 × 10⁻⁴ M Pb(NO₃)₂ with 1.0 × 10⁻³ M NaI; Qc = 1.0 × 10⁻¹⁰, Ksp = 7.1 × 10⁻⁹ → Qc Ksp, no precipitate), entropy comparison (1 mole N₂ at 1 atm has greater entropy than at 2 atm due to less compression), entropy change for H₂O(s) → H₂O(l) (increase in entropy because liquid has more available motions than solid), calculation of ΔS° for 2C₂H₆(g) + 7O₂(g) → 4CO₂(g) + 6H₂O(g) using standard entropy values (ΔS° = +89.5 J/mol – positive, more disorder), calculation of ΔG° for same reaction using standard free energies of formation (ΔG° = –2883.4 kJ/mol – spontaneous), calculation of ΔG° for C₂H₆(g) → C₂H₂(g) + 2H₂(g) at 25°C (ΔG° = +242.1 kJ/mol – nonspontaneous) and at 900°C (ΔG° = +38.56 kJ/mol – still nonspontaneous but less positive), coupling reactions (MnS(s) → Mn(s) + S(g) ΔG° = +214.2 kJ with S(s) + O₂(g) → SO₂(g) ΔG° = –300.1 kJ → overall MnS(s) + O₂(g) → Mn(s) + SO₂(g) ΔG° = –85.9 kJ – spontaneous), and AgBr precipitation prediction (mixing 1.0 × 10⁻⁶ M AgNO₃ with 1.0 × 10⁻⁶ M NaBr; Qc = 1.0 × 10⁻¹², Ksp AgBr = 5.0 × 10⁻¹³ → Qc Ksp, white precipitate forms → tube E). Suitable for college chemistry students learning solubility equilibria, Ksp, entropy, Gibbs free energy, and reaction spontaneity.