HW 3B
1. Write the Ideal Gas Law. What is the value for R? What are the units of R?
2. What is the pressure on an ideal gas if 0.25 moles of it occupies 3 L at 300 K?
3. What volume does 50 grams of CO2 occupy if it is at 0oC and 700 mm Hg?
4. How many grams of CH4 are present if 300 mL of it is at 120 kPa and -25 oC?
5. What is the density of H2 gas at STP?
6. What is the density of air (assume 80% N2 and 20% O2) at STP?
7. What is the density of Xe gas at 22 oC and 740 mm Hg?
8. What is the molecular weight of a gas if 2.3 grams of it occupy 230 mL at a pressure of 750 mm
Hg and a temperature of 75 oC?
9. A gas is 11.8% C, 69.6% Cl and 18.6% F. If 0.107 grams of it fills a 458 mL flask at 25 oC
at a pressure of 21.3 mm Hg, what is the molecular formula of the compound?
10. A gas is 25.2% S and 74.8% F. If 0.0955 g are put in an 89 mL flask at 45 oC and a pressure of
83.8 mm Hg, what is the molecular formula of the gas?
11. State Dalton’s Law of Partial Pressures.
12. A container has 0.5 atm of H2, 2.5 atm of He, and 3 atm of O2. What is the Ptotal in the
container?
13. A container has 10 grams of N2, 100 grams of Xe, and 42 grams of Ar. What is the Ptot in
the container if the volume is 4 L and the temperature is 50 oC?
14. A container has 20 grams of O2, 40 grams of CH4, and 10 grams of He at a Ptot of 600 mm
Hg. What is the partial pressure of each gas?
15. Which of the following gases would be nearly impossible to collect over water? Why?
N2, HCl, NH3, Cl2
16. Hydrogen gas is collected over water at 15 oC. If the gas was collected at 800 mm Hg
atmospheric pressure, what pressure of H2 gas was collected?
17. Oxygen gas is collected over water at 22 oC. If the gas was collected in a 250 mL container at
740 mm Hg atmospheric pressure, how many grams of oxygen were collected?
18. Convert a 3 m solution of CH3OH to mole fraction.
19. Convert a 5.6 PPM solution of Li+ to mass %.
20. You dissolve 25 grams of C10H16O in 350 mL of C2H5OH (density 0.785 g/mL). Calculate the
mole fraction, and mass %.
21. Concentrated HCl is 12 M and has a density of 1.18 g/mL. Calculate the mass % of the HCl in
the solution.