Table of contents

1. Intro to General Chemistry3h 48m
2. Atoms & Elements4h 16m
3. Chemical Reactions4h 10m
4. BONUS: Lab Techniques and Procedures1h 38m
5. BONUS: Mathematical Operations and Functions48m
6. Chemical Quantities & Aqueous Reactions3h 53m
7. Gases3h 49m
8. Thermochemistry2h 37m
9. Quantum Mechanics2h 58m
10. Periodic Properties of the Elements3h 9m
11. Bonding & Molecular Structure3h 29m
12. Molecular Shapes & Valence Bond Theory1h 57m
13. Liquids, Solids & Intermolecular Forces2h 23m
14. Solutions3h 1m
15. Chemical Kinetics2h 53m
16. Chemical Equilibrium2h 29m
17. Acid and Base Equilibrium5h 1m
18. Aqueous Equilibrium4h 47m
19. Chemical Thermodynamics1h 50m
20. Electrochemistry2h 42m
21. Nuclear Chemistry2h 36m
22. Organic Chemistry5h 7m
23. Chemistry of the Nonmetals2h 39m
24. Transition Metals and Coordination Compounds3h 16m

8. Thermochemistry

Hess's Law

General Chemistry

8. Thermochemistry

Hess's Law

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Multiple Choice

Using Hess's Law, calculate the enthalpy change for the reaction: 2 Cl(g) + O2(g) → 2 ClO2(g), given that a chlorine-oxygen bond in ClO2(g) has an enthalpy of 243 kJ/mol, an oxygen-oxygen bond has an enthalpy of 498 kJ/mol, and the standard enthalpy of formation of ClO2(g) is ΔH°f = 102.5 kJ/mol.

243 kJ/mol

205 kJ/mol

486 kJ/mol

102.5 kJ/mol

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Verified step by step guidance

Identify the target reaction: 2 Cl(g) + O2(g) → 2 ClO2(g). We need to find the enthalpy change for this reaction using Hess's Law.

Write the formation reaction for ClO2(g): Cl2(g) + O2(g) → 2 ClO2(g). The standard enthalpy of formation (ΔH°f) for ClO2(g) is given as 102.5 kJ/mol.

Use the given bond enthalpies: The enthalpy for a chlorine-oxygen bond in ClO2(g) is 243 kJ/mol, and the enthalpy for an oxygen-oxygen bond is 498 kJ/mol. These values will help in calculating the enthalpy changes for breaking and forming bonds.

Apply Hess's Law: The enthalpy change for the reaction can be calculated by considering the enthalpy changes for breaking the bonds in the reactants and forming the bonds in the products. Use the formula: ΔH = Σ(ΔH bonds broken) - Σ(ΔH bonds formed).

Calculate the total enthalpy change: Substitute the bond enthalpies into the formula and solve for the enthalpy change of the reaction. Remember to account for the stoichiometry of the reaction when calculating the total bond enthalpies.