3.4 Ideal Gas Law

The gas laws describe:

How the properties of a gas respond under changing conditions.

What are the three gas laws?

Boyle’s law, Charles’s law, Avogadro’s law

Relationship in Boyle’s law:

As gas pressure increases, gas volume decreases

Boyle’s Law formula:

P1V1=P2V2

Relationship in Charles’s law:

As gas temperature increases, gas volume increases

Charles’s law formula:

V1/T1 = V2/T2

Relationship in Avogadro’s Law:

As the number of moles of a gas increases, gas volume increases

Avogadro’s Law formula:

V1/n1 = V2/n2

Formula for ideal gas law:

PV=nRT (P = pressure in atm, V = volume in L, n = moles of gas, R = universal gas constant (0.08206 L atm / mol K), T = temperature in Kelvin)

Ideal gas law is used to relate:

Pressure, volume, moles, and temperature of a sample of gas

How does ideal gas law relate the pressure, volume, moles, and temperature of a sample of gas?

By using the gas constant R

How to convert Celsius to Kelvin?

Add 273.15 degrees

How many R values are listed on the equation sheet?

Several

The different R values differ in:

Units for pressure

When completing an Ideal Gas law calculation you have to make sure that:

Units all cancel out

How to make sure that all units cancel out when completing an Ideal Gas law calculation?

Check units

The ideal gas formula can be used to solve for _____ of a gas

Molar mass or density

Equation for using Ideal Gas formula to solve for molar mass or density of gas:

Molar mass = (Density (g/L) x R x Kelvin Temperature) / Pressure

According to Dalton's Law of Partial Pressure, the sum of all the partial pressures of each gas in a mixture of gasses is equal to:

The total pressure

According to Dalton's Law of Partial Pressure, ______ is equal to the total pressure

The sum of all the partial pressures of each gas in a mixture of gasses

How to express Dalton’s Law of Partial Pressure in mathematical notation?

P = PA + PB + PC... where A, B, and C are different gasses

Dalton’s Law of Partial Pressures is often used when:

Gases are collected “over water”

What happens as gases are collected over water?

As the gas is produced, the water is displaced and the water in the inverted vessel will empty while the gas is collected.

Advantages of using the method of collecting gas over water:

Allows for the gas to be measured and minimizes the amount of room air that contaminates the sample

Drawback of collecting gas over water:

As the gas travels through the water it will pick up water vapor which will contribute to the gas produced

When collecting gas over water, the amount of water vapor that is picked up is a function of the:

Temperature of the gas

When collecting gas over water, the water vapor that is picked up can be:

Subtracted using Dalton’s law of partial pressures.

In an experiment of collecting gas over water, when the water vapor is subtracted out the gas is described as:

Dry

Mole fraction is denoted by:

χA

χA means:

Moles A / Total moles

If a mixture is 3.0 mol O2 and 4.0 mol H2, the mole fraction of O2 =

3.0 moles/(3.0+4.0 moles)

How to find partial pressure?

Multiply mole fraction by total pressure of mixture