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

Endothermic & Exothermic Reactions

General Chemistry

8. Thermochemistry

Endothermic & Exothermic Reactions

Previous problemNext problem

Struggling with General Chemistry?

Join thousands of students who trust us to help them ace their exams!Watch the first video

Multiple Choice

How much energy (in kilojoules) is released when 32.5 g of ethanol vapor at 99.0 °C is cooled to -10.0 °C? Ethanol has a melting point of -114.5 °C, boiling point of 78.4 °C, ΔHvap = 38.56 kJ/mol, and ΔHfusion = 4.60 kJ/mol. The molar heat capacity is 113 J/(K·mol).

18.67 kJ

5.23 kJ

25.89 kJ

12.45 kJ

Previous problemNext problem

Verified step by step guidance

Calculate the number of moles of ethanol using its molar mass. The molar mass of ethanol (C2H5OH) is approximately 46.08 g/mol. Use the formula: \( \text{moles} = \frac{\text{mass}}{\text{molar mass}} \).

Determine the energy released during the cooling of ethanol vapor from 99.0 °C to its boiling point at 78.4 °C using the formula: \( q = m \cdot C \cdot \Delta T \), where \( m \) is the number of moles, \( C \) is the molar heat capacity, and \( \Delta T \) is the change in temperature.

Calculate the energy released during the phase change from vapor to liquid at the boiling point using the enthalpy of vaporization: \( q = n \cdot \Delta H_{\text{vap}} \), where \( n \) is the number of moles and \( \Delta H_{\text{vap}} \) is the enthalpy of vaporization.

Determine the energy released during the cooling of liquid ethanol from 78.4 °C to its melting point at -114.5 °C using the formula: \( q = m \cdot C \cdot \Delta T \).

Calculate the energy released during the phase change from liquid to solid at the melting point using the enthalpy of fusion: \( q = n \cdot \Delta H_{\text{fusion}} \). Finally, sum all the energy changes to find the total energy released.