U13: Day 5 WS - Laws: Dalton, Graham and Real vs. Ideal Gases

Explain Dalton’s Law of Partial Pressures.

• The total pressure within a container of a mixture of gases is equal to the sum of the partial pressure of each gas.

• The partial pressure of a gas is always less than the vapor pressure of water at the same temperature.

• Dalton’s Law states that the pressure of a gas mixture is always less than the pressure of the most abundant gas.

• Dalton’s Law applies only to solids and liquids, not gases.

Determine the total pressure of a gas mixture that contains O2, N2, and He, if the partial pressure of the gases are: P(O2) = 200 mm Hg, P(N2) = 350 mm Hg, P(He2) = 428 mm Hg.

• Ptotal = 978 mm Hg

• Ptotal = 800 mm Hg

• Ptotal = 600 mm Hg

• Ptotal = 500 mm Hg

Air is made up mostly of O2, N2, and CO2. If the total pressure of air is 765 mmHg and P(N2) = 0.79 atm and P(CO2) = 0.05 atm, then what is the partial pressure of the O2?

• PO2 = 0.17 atm

• PO2 = 0.25 atm

• PO2 = 0.10 atm

• PO2 = 0.05 atm

A mixture of hydrogen and oxygen gases has a total pressure of 5.50 atm. What is the partial pressure of the hydrogen if the P(O2) = 1250 mm Hg?

• PH2 = 2930 mm Hg

• PH2 = 1250 mm Hg

• PH2 = 4180 mm Hg

• PH2 = 5500 mm Hg

Explain the difference between diffusion and effusion.

• Diffusion is the ability of a gas to spread out in all directions. Effusion is the rate at which a gas escapes from a tiny pinhole in a container.

• Diffusion is the process of a liquid turning into a gas, while effusion is the process of a solid turning into a liquid.

• Diffusion is the movement of solids through liquids, while effusion is the movement of liquids through solids.

• Diffusion is the rate at which a gas escapes from a container, while effusion is the ability of a gas to spread out in all directions.

What is the equation for Graham’s law of effusion?

• Rate A / Rate B = sqrt(MM_B / MM_A)

• Rate A / Rate B = sqrt(MM_A / MM_B)

• Rate A / Rate B = MM_A / MM_B

• Rate A / Rate B = MM_B / MM_A

Explain how the molar mass of a gas will affect the rate of effusion for that gas.

• Higher molar mass: effusion rate is slower. Lower molar mass: effusion rate is faster.

• Higher molar mass: effusion rate is faster. Lower molar mass: effusion rate is slower.

• Molar mass does not affect the rate of effusion for a gas.

• Both higher and lower molar mass gases effuse at the same rate.

Compare the rates of effusion for hydrogen and oxygen gases.

Compare the rates of effusion for carbon monoxide and carbon dioxide gases.

• CO will effuse more quickly due to a lower molar mass than CO2. CO is 1.253x faster.

• CO2 will effuse more quickly due to a lower molar mass than CO. CO2 is 1.253x faster.

• CO and CO2 will effuse at the same rate because they have similar molar masses.

• CO will effuse more quickly due to a lower molar mass than CO2. CO is 0.797x faster.

What is an ideal gas and how does it differ from a real gas? Name three factors which will cause a gas to deviate from ideal behavior.

• An ideal gas is assumed to have no molecular volume and no attractive forces. However, ideal gases do not exist. Lower temperature, high molar masses, high pressures, and polar molecules will cause gases to deviate from ideal behavior.

• An ideal gas is one that has a definite volume and strong intermolecular forces. Real gases always behave ideally at all conditions. High temperature, low pressure, and non-polar molecules cause deviation from ideal behavior.

• An ideal gas is a gas that can be liquefied easily. Real gases cannot be compressed. Low temperature, low molar masses, and low pressures cause deviation from ideal behavior.

• An ideal gas is a gas that reacts with other gases. Real gases do not react. High temperature, high molar masses, and high pressures cause deviation from ideal behavior.