# Enthalpy Changes and Calorimetry

*Time: 20 min. 6 questions.*

## Instructions

Answer all six questions. For multiple choice, select the best answer. For short answer, write a complete sentence or brief explanation. For true or false, write True or False. For numeric questions, show your calculation and include units. You may use a calculator.

## Questions

1. A student burns 2.0 g of sugar in a calorimeter and measures a temperature increase of 8.5 °C in 100 g of water. The specific heat capacity of water is 4.18 J/(g·°C). Calculate the heat released by the sugar, in joules. ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23634))

2. True or false: A negative ΔH value indicates an endothermic reaction. ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23638))

3. Which of the following best describes molar enthalpy?
A) The total energy released when one mole of a substance burns
B) The energy change per mole of reactant or product in a chemical reaction
C) The temperature increase of water in a calorimeter
D) The specific heat capacity of a substance multiplied by its mass
([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23636))

4. In a calorimetry experiment, 50 mL of 1.0 M HCl is mixed with 50 mL of 1.0 M NaOH. The temperature of the solution increases from 20.5 °C to 27.3 °C. The mass of the solution is 100 g and its specific heat capacity is 4.18 J/(g·°C). Calculate the heat released by this neutralization reaction, in joules. ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23641))

5. A student uses calorimetry data from an experiment to determine that a combustion reaction releases 890 kJ per mole of fuel burned. What does this value represent? ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23641))

6. Multiple choice: Which equation is used to calculate the heat absorbed or released by a substance during a temperature change?
A) ΔH = q/n
B) Q = mcΔt
C) PV = nRT
D) E = hν
([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23634))

## Curriculum Coverage

| Question | Outcome | Description |
|----------|---------|-------------|
| 1 | [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23634) | Apply Q = mcΔt to heat transfer analysis |
| 2 | [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23638) | Interpret ΔH notation |
| 3 | [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23636) | Define enthalpy and molar enthalpy |
| 4 | [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23641) | Use calorimetry data to determine enthalpy changes |
| 5 | [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23641) | Use calorimetry data to determine enthalpy changes |
| 6 | [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23634) | Apply Q = mcΔt to heat transfer analysis |

## Answer Key

1. **3553 J (or 3.6 kJ)**, Q = mcΔt = 100 g × 4.18 J/(g·°C) × 8.5 °C = 3553 J; the heat released by the sugar equals the heat absorbed by the water.

2. **False**, A negative ΔH indicates an exothermic reaction; endothermic reactions have positive ΔH values.

3. **B**, Molar enthalpy is the energy change per mole of reactant or product, allowing comparison of reactions regardless of the amounts used.

4. **2842.4 J (or 2.8 kJ)**, Q = mcΔt = 100 g × 4.18 J/(g·°C) × (27.3 °C − 20.5 °C) = 100 × 4.18 × 6.8 = 2842.4 J ≈ 2.8 kJ; this is the heat released by the neutralization reaction.
5. **The molar enthalpy (or ΔH) of the combustion reaction**, The value represents the energy change per mole of fuel burned, expressed in kJ/mol, and is used to communicate the thermochemical properties of the reaction.

6. **B**, The equation Q = mcΔt relates the heat transferred to the mass, specific heat capacity, and temperature change of a substance.

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*AILI quiz · language en · model claude-haiku-4-5-20251001 · generated 2026-09-17 · id b60aa236-0bb1-460e-9bbe-ba4466094c7b*

### Sources

- node:n1: Chemistry › Chemistry (20, 30) › Chemistry 30 › Unit A: Thermochemical Changes › General Outcome 1 (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23636)
- node:n2: Chemistry › Chemistry (20, 30) › Chemistry 30 › Unit A: Thermochemical Changes › General Outcome 1 (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23634)
- node:n3: Chemistry › Chemistry (20, 30) › Chemistry 30 › Unit A: Thermochemical Changes › General Outcome 1 (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23641)
- node:n4: Chemistry › Chemistry (20, 30) › Chemistry 30 › Unit A: Thermochemical Changes › General Outcome 1 (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23634)
- node:n5: Chemistry › Chemistry (20, 30) › Chemistry 30 › Unit A: Thermochemical Changes › General Outcome 1 (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23636)
- resource:r1: Resources › type#activity › SCN3796 (https://goa-cc-uat-aili-app-001.azurewebsites.net/library/resource/9ykNTynh306g6EnZlkTITQ)
- node:n6: Chemistry › Chemistry (20, 30) › Chemistry 30 › Unit A: Thermochemical Changes (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23633)
- node:n7: Chemistry › Chemistry (20, 30) › Chemistry 30 › Unit A: Thermochemical Changes › General Outcome 1 (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23638)
- resource:r2: Resources › type#activity › SCN3796 (https://goa-cc-uat-aili-app-001.azurewebsites.net/library/resource/0uxhxD914kqzmssVwCK4tg)