Calculate the approximate volume (in liters) of a 0.400 mol sample of gas at 20.0 °C and a pressure of 2.43 atm.

Example #1: A sample of gas at 25.0 °C has a volume of 11.0 L and exerts a pressure of 660.0 mmHg. How many moles of gas are in the sample?

Example #2: A sample of gas at 28.0 °C has a volume of 6.20 L and exerts a pressure of 720.0 mmHg. How many moles of gas are in the sample?

Example #3: Calculate the approximate volume of a 0.400 mol sample of gas at 11.0 °C and a pressure of 2.43 atm.

Example #4: Calculate the approximate temperature of a 0.300 mol sample of gas at 780. mmHg and a volume of 6.00 L.

Example #5: What is the pressure exerted by 2.3 mol of a gas with a temperature of 40. °C and a volume of 3.5 L?

Example #6: A sample of dry gas weighing 2.1025 grams is found to occupy 2.850 L at 22.00 °C and 740.0 mmHg. How many moles of the gas are present?

Example #7: Using the problem above, what is the molar mass of the gas?

Example #8: At STP, a 5.00 L flask filled with air has a mass of 543.251 g. The air in the flask is replaced with another gas and the mass of the flask is 566.107 g. The density of air is 1.29 g/L. What is the gas that replaced the air?

Example #9: A vessel at 25.0 °C is evacuated to a point where the amount of gas remaining is 5.00 x 109 molecules per m3. What is the pressure in the vessel?

Example #10: Of the following gases, which has density of 0.906 g/L at 315 K and 1.16 atm.

Example #11: A 0.105 g sample of an unknown diatomic gas contained in a 125 mL vessel has a pressure of 560 torr at 23 &175;C. What is the molar mass of the gas? What is the identity of the gas?

Example #12: If 1.0 g of each of the following gases is taken at STP, which one would occupy the greatest volume?

(a) CO

(b) H2O

(c) CH4

(d) NO

(e) They would all occupy the same volume.

Example #13: If 12.8 g of liquid helium at 1.7 K is completely vaporized. What volume does the helium occupy at STP?

Example #14: An elemental gas (meaning that it is made from one element) has a mass of 10.3 grams. It occupies 58.4 L at 1.00 atm and 2.50 °C. Identify the gas.

Example #15: An elemental gas (meaning that it is made from one element) has a mass of 10.3 grams. It occupies 4.27 L at 1.00 atm and 85.0 °C. Identify the gas.

Explanation:

n2(g) + 3h2-> 2nh3(g)   this is the balanced equation

note the mole ratio between n2, h2 and nh3.   it is 1 : 3 : 2   this will be important.

moles n2 present = 28.0 g n2 x 1 mole n2/28 g = 1 mole n2 present

moles h2 present = 25.0 g h2 x 1 mole h2/2 g = 12.5 moles h2 present

based on mole ratio, n2 is limiting in this situation because there is more than enough h2 but not enough n2.

moles nh3 that can be produced = 1 mole n2 x 2 moles nh3/mole n2 = 2 moles nh3 can be produced

grams of nh3 that can be produced = 2 moles nh3 x 17 g/mole = 34 grams of nh3 can be produced

note:   the key to this problem is recognizing that n2 is limiting, and therefore limits how much nh3 can be produced.

"the periodic table is arranged in order of atomic number."