1. Unit 7: Thermochemistry
Board Races

2. Measuring Heat
A food item contains 124 nutritional Calories. How many calories does the food item contain?
124 × 1000 = 124,000 calories

3. Measuring Heat
Ethanol is being used as an additive to gasoline. The combustion of 1 mole of ethanol releases 1367 kJ of energy. How many Calories are released?
1367 KJ
1 Calorie
= 327 Calories
4.184 kJ

4. Measuring Heat
To vaporize 2.00 g of ammonia, 656 calories are required. How many kilojoules are required?
656 cal
4.184 J
1 kJ
= 2.74 kJ
1 cal
1000 J

5. Measuring Heat
A 25.0 g bolt made of an alloy absorbed 250 J of heat as its temperature changed from 25.0ºC to 78.0ºC. What is the specific heat of the alloy? (units are J/g•ºC)
78.0ºC – 25.0ºC = 53.0ºC
250 J
=0.189 J/g•ºC
25.0 g • 53.0ºC

6. Measuring Heat
How many joules of heat are lost by kg of granite as it cools from 41.2ºC to -12.9ºC? The specific heat of granite is J/g•ºC. (Watch your units!)
-12.9ºC –3580 × 1000 = 3,580,000 g
41.2ºC = -54.1ºC
q = (3,580,000 g)(0.803 J/g•ºC)(54.1ºC)
q = 1.56×108 J

7. Measuring Heat
How much heat is absorbed by a g piece of lead when its temperature increases by 65.4ºC? (specific heat of lead is J/g•ºC)
q = (44.7 g)(0.129 J/g•ºC)(65.4ºC)
q = 377 J

8. Measuring Heat
When 10.2 g of canola oil at 25ºC is places in a wok, 3.34 kJ of heat is required to heat is to a temperature of ºC. What is the specific heat of canola oil?
3.34 kJ × 1000 = 3340 J
196.4ºC - 25ºC = 171.4ºC
C = 1.91 J/g•ºC
C = q
3340 J
g • ΔT
10.2 g•171.4ºC