Gases

Vocabulary

100

The model that describes how ideal gases behave is called the...

kinetic molecular theory

200

The movement of a gas particle through a small hole is called...

effusion

300

What is an elastic collision?

a collision where no net kinetic energy was lost

400

Describe "vapor pressure".

the pressure of a gas when the gas is in equilibrium with its liquid state

500

Define "mole fraction" in unambiguous terms.

the decimal value or percentage or fraction of one substance by mole within a mixture

Miscellaneous

100

True/False: Pressure is a measure of the number of collisions.

False

Number of collisions impacts pressure, but pressure is a measure of the force exerted across a surface area.

200

In what direction does air flow?

From high to low pressure (net)

300

Describe the distribution of gases throughout the Earth's atmosphere.

Gases are more densely concentrated near the surface of the Earth and are scarcer as altitude increases.

400

What are the values and units for STP?

1 atm and 0 ^oC

500

Provide two differences between a real and an ideal gas.

Some options:

Real gases undergoes inelastic collisions, ideal gases undergo elastic.

Ideal gases don't really exist whereas real gases do.

Ideal gases don't attract/repel each other whereas real gases.

Gas Laws & Equipment

100

What unit(s) of temperature can be used with gas laws?

Kelvin only

200

Write a math equation to express the relationship between mole fraction and partial pressure.

P_A = X_A * P_total

300

Which law states that temperature and pressure are directly proportional?

Gay-Lussac's law (P₁ / T₁ = P₂ / T₂)

400

Draw the set-up for a mercury barometer.  Include a depiction of how you would interpret it.

*drawn on board*

500

Which gas laws were mathematically, rather than experimentally, determined?

combined gas law and ideal gas law

Calculations I

100

Convert 91 torr to mmHg.

91 mmHg

200

An experiment called for 4.83 L of sulfur dioxide, SO₂, at 200. K.  What volume of this gas would be needed at 300. K (assuming constant pressure)?

7.25 L

300

If a sample of H₂ gas has a volume of 8.62 mL at a temperature of 35 ℃, calculate the volume occupied by the gas if its temperature were raised to 135 ℃.

11.4 mL

400

What is the volume of 23.5 grams of nitrogen at STP?

23.5 g * (mol / 28.0134 g) * (22.4 L / mol) = 18.8 L

500

A scuba tank has a pressure of 195 atm at a temperature of 10. ℃. If the volume of the tank is 350 L, how many moles of oxygen are in the tank?  Oxygen is 21 % by mole of air.

n_air = (195 atm) * (350 L) / [(283 K) * (0.08206 atmL/molK)] = 2,939 mol

n_oxygen = 0.21 * 2,939 mol = 620 mol

Calculations II

100

Convert 6.3 kPa to atm.

6.3 kPa * (atm / 101.325 kPa) = 0.062 atm

200

9.5 L of a gas was at an unknown pressure. However, at standard pressure, its volume was measured to be 8.5 L. What was the unknown pressure?

(9.5 L) * P = (8.5 L) * (1 atm)

P = 0.89 atm

300

How many moles of oxygen occupy 4.2 L at 298 K and 2.00 atm?

n = (2.00 atm) * (4.2 L) / [(298 K) * (0.08206 atmL/molK)] = 0.34 mol

400

If 78 % of air is nitrogen by volume, how many moles of nitrogen are in a 25 L sample of air at STP?

25 L * (mol_air / 22.4 L) * (78 mol_nitrogen / 100 mol_air) = 0.87 mol

500

Final Question:

When magnesium reacts with hydrochloric acid, hydrogen gas is produced.  Calculate the volume of hydrogen gas produced at STP by reacting 5.00 g Mg with an excess of HCl.

Mg_(s) + 2 HCl_(aq) → MgCl_2(aq) + H_2(g)

5.00 g Mg * (1 mol Mg / 24.305 g) * (1 mol H₂ / 1 mol Mg) * (22.4 L / 1 mol H₂) = 4.61 L