CHEMISTRY 21A
Instructor: Dr. Dragan Marinkovic
Assignment #7
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1. a) compressibility is:
b) formula for density is (explain nthe components of the formula):
c) equation for kinetic energy is (explain nthe components of the equation):
d) potential energy is:
e) cohesive force is:
f) disruptive force is:
2. What are the most common units for pressure and what is their relation i.e. conversion factors)?
3. What is STP (standard conditions)? What are the numerical values for STP?
CHEMISTRY 21A
Instructor: Dr. Dragan Marinkovic
Assignment #7
4. What is:
a) evaporation (vaporization)?
b) vapor pressure?
c) normal (standard) boiling point?
d) sublimation?
e) specific heat?
f) heat of fusion?
g) heat of vaporization?
h) volume of 1 mole of a gas at STP?
5. A chemist reads a pressure from a manometer attached to an experiment as 36.2 cm/Hg. Calculate this pressure in the
following units:
a) atm
b) mm/Hg
c) Torr
d) psi
6. Write three (out of five) postulates of the Kinetic Molecular Theory.
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CHEMISTRY 21A
Instructor: Dr. Dragan Marinkovic
Assignment #7
7. Explain the Dalton’s Law of Partial Pressures.
8. Convert the following temperatures from the units given to the units indicated:
a) The melting poing of potassium metal, 63.7oC to Kelvins
b) The freezing point of liquid hydrogen, 14.1 K to degrees Celsius
c) The boiling point of liquid helium, -268.9oC to Kelvins
9. A 5.00 L gas sample is collected ata temperature of 27.0oC and pressure of 1.20 atm. The gas is to be transvered to a
3.00 L container at a pressure of 1.00 atm. What will be the temperature of the gas in Celsius degrees?
10. Use the Ideal Gas Law to calculate the following:
a) The number of moles of argon in a gas sample that occupies a volume of 400 mL at a temperature of
90oC and has a pressure of 735 Torr.
b) The pressure in atm exerted by 0.750 mol of hydrogen gas confined to a volume of 2600 mL at 50oC.
c) The volume in liters of a tank of nitrogen if 1.50 mol af the gas exerts pressure of 4.32 atm at 20.0 oC.
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CHEMISTRY 21A
Instructor: Dr. Dragan Marinkovic
Assignment #7
11. A sample of gas weighs 0.176 g and has a volume of 114.0 mL at a pressure of 640 Torr and a temperature of 20 oC.
Determine the molecular weight of the gas and identify it as CO2, O2, or CO.
12. Calculate the total amount of heat needed to change 500 g of ice at -10oC into 500 g of steam at 120oC. Do this by
calculating the heat required for each of the following steps and adding to get the total:
Step 1: ice (-10oC → 0oC)
Step 2: ice (0oC) → water (0oC)
Step 3: water (0oC) → water (100oC)
Step 4: water (100oC) → steam (100oC)
Ste5 5: steam (100oC) → steam (120oC)
13. The pressure gauge of a steel cylinder of methane gas (CH4) reads 400 psi. The cylinder has a volume of 1.50 dm3
and is at a temperature of 30.0oC. How many grams of methane does the cylinder contain?
14. Methylene chloride (CH2Cl2) was used at one time as local anesthetic by dentists. It was sprayed onto the area to be
anesthetized. Propose the explanation of how it worked (Hint: b.p. of CH2Cl2 is 40oC).
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