# 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 the word True or False and correct any false statement. For numeric questions, show your calculation and include units in your final answer.

## Questions

1. Enthalpy is best defined as:

A) the total kinetic energy of all particles in a system
B) the heat content of a system at constant pressure
C) the rate at which a chemical reaction proceeds
D) the energy required to break all bonds in a molecule

([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23636))

2. True or false: A negative value for ΔH indicates that a reaction absorbs heat from the surroundings.
([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23638))

3. In a calorimetry experiment, 50.0 mL of 2.0 mol/L hydrochloric acid is mixed with 50.0 mL of 2.0 mol/L sodium hydroxide solution in an insulated cup. The temperature of the mixture rises from 21.0°C to 28.5°C. Assuming the density and specific heat capacity of the solution are 1.0 g/mL and 4.18 J/(g·°C) respectively, calculate the heat released by this neutralization reaction in joules.
([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23641))

4. Which of the following statements correctly describes the relationship between heat transfer and the variables in Q = mcΔt?

A) Heat transfer is inversely proportional to mass and temperature change
B) Heat transfer is directly proportional to mass, specific heat capacity, and temperature change
C) Heat transfer depends only on the specific heat capacity of the substance
D) Heat transfer is independent of the temperature change in the system

([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23634))

5. Explain the difference between enthalpy (ΔH) and heat (Q) as measured in a calorimetry experiment.
([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23641))

6. What is the specific heat capacity of a substance if 2500 J of heat energy raises the temperature of 100 g of the substance by 5°C?
([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23634))

## Curriculum Coverage

| Question | Outcome Alias | Outcome Description |
|---|---|---|
| 1 | [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23636) | Define enthalpy and molar enthalpy for chemical reactions |
| 2 | [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23638) | Use and interpret ΔH notation to communicate and calculate energy changes |
| 3 | [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23641) | Use calorimetry data to determine the enthalpy changes in chemical reactions |
| 4 | [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23634) | Recall the application of Q = mcΔt to the analysis of heat transfer |
| 5 | [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23641) | Use calorimetry data to determine the enthalpy changes in chemical reactions |
| 6 | [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23634) | Recall the application of Q = mcΔt to the analysis of heat transfer |

## Answer Key

1. **B) the heat content of a system at constant pressure**
Enthalpy is defined as the heat content of a system measured at constant pressure, which is the standard condition for most chemical reactions in the laboratory ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23636)).

2. **False. A negative value for ΔH indicates that a reaction releases heat to the surroundings (is exothermic).**
The ΔH notation uses negative values for exothermic reactions and positive values for endothermic reactions ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23638)).

3. **3,135 J (or 3.14 kJ)**
Total mass of solution = 50.0 g + 50.0 g = 100.0 g; ΔT = 28.5 − 21.0 = 7.5°C; Q = mcΔt = 100.0 g × 4.18 J/(g·°C) × 7.5°C = 3,135 J ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23641)).

4. **B) Heat transfer is directly proportional to mass, specific heat capacity, and temperature change**
The equation Q = mcΔt shows that heat is directly proportional to all three variables: mass (m), specific heat capacity (c), and temperature change (ΔT) ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23634)).

5. **In calorimetry, Q is the heat measured by the calorimeter as energy transfers between the reaction and the water, while ΔH is the enthalpy change of the chemical reaction itself at constant pressure; Q measured in the calorimeter approximates ΔH when the calorimeter is well-insulated and heat loss to the surroundings is minimized.**
Heat (Q) is the experimental measurement obtained from calorimetry data using Q = mcΔt, whereas ΔH is the thermodynamic property of the reaction and represents the enthalpy change under standard conditions ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23641)).

6. **5 J/(g·°C)**
Using Q = mcΔt, rearranged to c = Q/(mΔt) = 2500 J / (100 g × 5°C) = 5 J/(g·°C) ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23634)).

---
*AILI quiz · language en · model claude-haiku-4-5-20251001 · generated 2026-09-17 · id 15e70b97-2d2a-498f-a212-b96c2c462417*

### 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#studentsupport, type#teachersupport › SCN3796 (https://goa-cc-uat-aili-app-001.azurewebsites.net/library/resource/YlIUl7k3G0y6R-b8XyPAGw)
- resource:r2: 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 › General Outcome 1 (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23638)
- 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/23648)
- resource:r3: Resources › type#activity › SCN3796 (https://goa-cc-uat-aili-app-001.azurewebsites.net/library/resource/0uxhxD914kqzmssVwCK4tg)