CPA Chemistry Enthalpy Problems

University:
Princeton University
Course:
FRS 172 | Origins of Modern Communications and the Principles of Innovation
Academic year:

2024
Views:

213

Pages:

2
Author:

Naaviv XDE

CPA Chemistry Enthalpy Problems Vivaan Pande Name: ____________________ 4A 3/11/2026 Date: __________ Period: ____ Enthalpy Problems 1. How much heat will be released when 6.44 g of sulfur reacts with excess O2 according to the following equation? 2 S + 3 O2 → 2 SO3 H = – 791.4 kJ 6.44 g S (1 mol S / 32.06 g S) (−791.4 kJ / 2 mol S) = −79.6 kJ 2. How much heat will be released when 4.72 g of carbon reacts with excess O2 according to the following equation? C + O2 → CO2 H = – 393.5 kJ 4.72 g C (1 mol C / 12.01 g C) (−393.5 kJ / 1 mol C) = −154.7 kJ 3. How much heat will be absorbed when 38.2 g of bromine reacts with excess H2 according to the following equation? H2 + Br2 → 2 HBr H = 72.80 kJ 38.2 g Br₂ (1 mol Br₂ / 159.8 g Br₂) (72.8 kJ / 1 mol Br₂) = 17.4 kJ 4. How many moles of chlorine are required to react with excess phosphorus in order to release 13.7 kJ of energy? 2 P + 5 Cl2 → 2 PCl5 H = – 886 kJ 13.7 kJ (5 mol Cl₂ / 886 kJ) = 0.0773 mol Cl₂ 5. How many grams of ethanol (C2H5OH) are needed to react with excess O2 in order to release 142 kJ of energy? C2H5OH + 3 O2 → 2 CO2 + 3 H2O 142 kJ (1 mol C₂H₅OH / 1366.7 kJ) (46.07 g / 1 mol) = 4.79 g C₂H₅OH H = – 1366.7 kJ 6. How much heat will be absorbed when 13.7 g of nitrogen reacts with excess O2 according to the following equation? N2 + O2 → 2 NO H = 180 kJ 13.7 g N₂ (1 mol N₂ / 28.02 g N₂) (180 kJ / 1 mol N₂) = 88.0 kJ 7. How many grams of iron are needed to react with excess O2 in order to release 78.8 kJ of energy? 3 Fe + 2 O2 → Fe3O4 H = – 1120.48 kJ 78.8 kJ (3 mol Fe / 1120.48 kJ) (55.85 g / 1 mol Fe) = 11.8 g Fe 8. How many grams of hydrogen are required to react with excess O2 in order to release 2660 kJ of energy? 2 H2 + O2 → 2 H2O H = – 571.6 kJ 2660 kJ (2 mol H₂ / 571.6 kJ) (2.016 g / 1 mol H₂) = 18.8 g H₂ 9. How much heat will be transferred when 14.9 g of ammonia reacts with excess O2 according to the following equation? Is this reaction endothermic or exothermic? 4 NH3 + 5 O2 → 4 NO + 6 H2O H = – 1170 kJ 14.9 g NH₃ (1 mol NH₃ / 17.03 g NH₃) (−1170 kJ / 4 mol NH₃) = −256 kJ, Exothermic 10. How much heat will be transferred when 5.81 g of graphite reacts with excess H2 according to the following equation? Is this reaction endothermic or exothermic? 6 C (graphite) + 3 H2 → C6H6 H = 49.03 kJ 5.81 g C (1 mol C / 12.01 g C) (49.03 kJ / 6 mol C) = 3.95 kJ, Endothermic