CHEM 051 Los Angeles Southwest College Chapter 2 Matter and Energy Questions

Los Angeles Southwest CollegeChemistry 051 – Fundamental of Chemistry
Instructor: Prof. Rodriguez, SP2023
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Date:
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Homework #2
You must show your entire work on a separate sheet(s) of paper to get full credit.
1. Convert the following Temperature to fill in the blanks.
K
a.
b.
c.
o
C
o
F
22.19
-30.55
547.8
2. a. A sample of water with a mass of 23.31 g and an initial temperature of 367.67 K
loses 8615 Joules. What is the final temperature?
b. A sample of water with a mass of 764.1g undergoes a temperature change from
41.23oC to 20.82oC. What is the heat change in Joules?
3. A typical diet in the United States provides 15% of the calories from protein, 45%
from carbohydrates, and the remainder from fats. Calculate the grams of protein,
carbohydrate, and fat to be included each day in diets having the following caloric
requirements.
a. 1200 kcal
b. 1900 kcal
c. 2600 kcal
4. a. One liquid has a temperature of 140oF and another liquid has a temperature of 60oC.
Are the liquids at the same temperature or at different temperatures?
b. What is Kinetic energy?
c. What is Potential energy?
5. Identify each of the following changes of state as melting, freezing, or sublimation.
a. Dry ice in an ice-cream cart disappears.
b. Snow on the ground turns to liquid water.
c. Heat is removed from 125 g of liquid water to 0oC.
6. Identify each of the following changes of state as evaporation, boiling, or
condensation:
a. At 100oC, the water in a pan changes to steam.
b. On a cool morning, the windows in your car fog up.
c. A shallow pond dries up in the summer.
d. Your teakettle whistles when the water is ready for tea.
7. Calculate the heat needed at 0oC to make each of the following changes of state.
Indicate whether heat was absorbed or released.
a. calories to freeze 35 g of water.
b. calories to freeze 250 g of water.
c. kilocalories to melt 140 g of ice.
8. Draw a cooling curve for a sample of steam that cools from 110oC to -10oC. Indicate
the segment of the graph that corresponds to each of the following:
a. solid
b. freezing point
c. liquid
d. condensation point (boiling point)
e. gas
9. Calculate the quantity of heat in kJ, associated with a 33.5oC decrease in temperature
in a 5.85 kg aluminum bar (specific heat of aluminum=0.903 J g -1 oC-1)