1. WS: Calorimetry Problems

2. 1. How much energy is needed to change the temperature of 50
1. How much energy is needed to change the temperature of 50.0 g of water 15.0 oC?
Q = m x s x T
Q = (50.0g)(4.18 J/g oC)(15.0 oC)
= 3135 J

3. 2. How many grams of water can be heated from 20.0 oC to 75oC using 12.5 kilojoules?
m = Q/s x T
12.5 kJ (1000 J/1kJ) = 12,500 J
T = (75oC - 20oC) = 55oC
m = (12,500 J)/(4.18 J/g oC)(55.0 oC)
= 54.4 g

4. 3. What is the final temperature after 840 Joules is absorbed by 10
3. What is the final temperature after 840 Joules is absorbed by 10.0 g of water at 25.0 oC?
T = Q/m x s
T = (840 J)/(10.0 g)(4.18 J/g oC)
= 20.1 ºC
25 ºC ºC = 45.1 ºC

5. 4a. How much energy is needed to raise the temperature of a 8
4a. How much energy is needed to raise the temperature of a 8.50 x 102g block of aluminum from 22.8oC to 94.6oC? (Al = 0.90 J/g oC)
Q = m x s x T
8.50 x 102 g = 850 g
T = (94.6 – 22.8) = 71.8 oC
Q = (850 g)(0.90 J/g oC)(71.8 oC)
= J or 54.9 kJ

6. 4b. What is the specific heat capacity of aluminum per mole?
Al = (0.90 J/g oC)(27.0 g/mol)
= 24.3 J/mol oC)

7. 5. A piece of metal weighing 59. 047 g was heated to 100
5. A piece of metal weighing g was heated to °C and then put it into mL of water (initially at 23.7 °C). The metal and water were allowed to come to an equilibrium temperature, determined to be 27.8 °C. Assuming no heat lost to the environment, calculate the specific heat of the metal.

8. 5. Determine heat gained by water: Q = m x s x T
Density of water = 1.0 g/ mL
Q = (100.0g)(4.18 J/g oC)(4.1 oC)
= 1714 J
Since no heat loss Qwater = Qmetal

9. 5. Determine specific heat of metal:
S = Q/m x T
T = 100 ºC – 27.8 ºC = 72.2 ºC
S = 1714 J/( g)(72.2 ºC)
= J/g ºC