General chemistryLesson 2 of 3 in the course Thermochemistry

Calorimetry: Heat Balances, Solution and Bomb Measurements

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

Calorimetry is the measurement of heat transferred to or from a substance. A system is the substance or substances undergoing the change being studied. The surroundings are everything else that can exchange heat with the system, including a solution, the calorimeter, and possibly the external environment.

Heat flows from a warmer object to a cooler one. For example, when a hot metal sample is placed in cool water, the metal loses heat while the water gains heat. Their temperatures move toward a shared final temperature, called thermal equilibrium.

All flashcards

What is thermal equilibrium?
The state in which objects in thermal contact share the same temperature and have no net heat flow between them.
What equation relates heat transfer to mass, specific heat, and temperature change?
q=mcΔTq=mc\Delta T, where ΔT=Tf−Ti\Delta T=T_f-T_i.
How are reaction heat and solution heat related in an ideal solution calorimeter?
qreaction=−qsolutionq_{reaction}=-q_{solution}, when heat absorbed by the calorimeter and external heat exchange are negligible.
What is a bomb calorimeter?
A constant-volume calorimeter in which a sample burns in oxygen inside a sealed vessel.
What is one nutritional Calorie equivalent to?
One kilocalorie, or 4,184 joules.

Quiz questions

  1. In an ideal insulated calorimeter, water gains 350 J from a metal sample. What is the metal's heat change?Answer: It loses 350 J, so its heat change is −350 J.
  2. Why is a bomb calorimeter calibrated with a reaction of known heat?Answer: To determine the calorimeter's overall heat capacity.
  3. Which description matches a bomb calorimeter?Answer: A sample burns in oxygen in a sealed vessel at constant volume.
  4. A food serving contains 5 g protein, 31 g carbohydrate, and 12 g fat. Using 4 Calories/g for protein and carbohydrate and 9 Calories/g for fat, what is its estimated energy?Answer: 252 Calories
  5. Why can specific heat alone be insufficient to identify an unknown metal?Answer: Different materials can have similar specific heat values.

Based on Chemistry 2e by Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson, PhD (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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