1. Thermochemistry
The branch of chemistry concerned with the quantities of heat evolved or absorbed during chemical reactions

9. Example Problem 15-1
Calculating Heat
A silver bar with a mass of g is heated from 22.0°C to 68.5°C.
How much heat does the silver bar absorb?
Use the equation for heat.
q = c x m x ∆T

10. The temperature change is the difference between the final temperature
and the initial temperature.
∆T = 68.5°C °C = 46.5°C
The specific heat of silver is
0.235 J/(g°C). Substitute the known values to solve for the amount
of heat absorbed.

11. q = J/(g°C) x g x 46.5°C = 2730 J

12. How much heat does a 23.0-g ice cube absorb as its temperature
increases from -17.4°C to 0.0°C? Give the answer in both
joules and calories.

13. 1674 J or 400 cal

14. A sample of an unknown metal has a mass of 120.7 g. As the
sample cools from 90.5°C to 25.7°C, it releases 7020 J of
energy. What is the specific heat of the sample?

15. Specific heat
J/(g°C). The specific heat
is very close to the value
for aluminum.

16. A 15.6-g sample of ethanol absorbs 868 J as it is heated. If the
initial temperature of the ethanol was 21.5°C, what is the final
temperature of the ethanol?

17. 44.3°C

18. Heat changes that occur during chemical and physical processes can be measured using an insulated device called a calorimeter. In one type of calorimeter, the temperature change of a known mass of water is used to determine the amount of energy released or

19. absorbed by a system undergoing a chemical or physical change.