All AP Chemistry Resources
Example Questions
Example Question #4 : Ideal Gas Law
If the pressure of a sample of one mole of an ideal gas is increased from 2atm to 3atm at a constant volume, and the initial temperature was 20˚C, what is the final temperature of the sample?
439.5K
195.3K
30K
303K
439.5K
Because the mass and volume of the sample of the ideal gas are kept constant, a change in pressure causes only a direct change in the temperature. This can be derived from the following ideal gas equation:.
Example Question #5 : Ideal Gas Law
How many moles of carbon dioxide occupy a space of 16 liters at a pressure of 760torr and a temperature of 250K?
We can calculate the number of moles using the ideal gas law:
Units always have to be in SI units: atm, liters, kelvin, etc. For this question, we have SI units for everything except for the pressure, which is given in torr, rather than atm.
Now that we have the proper units, we can use our given values for pressure, temperature, and volume to find the moles of gas present.
Example Question #2 : Ideal Gas Law
A 2mol sample of an ideal gas with a volume of 3L and temperature of 298K experiences a decrease in pressure of 4atm. If the mass and temperature remain constant, what is the final volume?
First, one must find the initial pressure by plugging the initial conditions into the ideal gas equation.
Decreasing this by 4 atm leads to a final pressure of 12.31atm, which one can plug into the ideal gas equation to find the final volume.
Because only the pressure and volume change, one can also use Boyle's law after finding the initial and final pressure values.
Example Question #41 : Phases Of Matter
A sample of chlorine gas fills a vessel at a temperature of . The vessel has a volume of 3L and experiences a pressure of 3atm. What is the mass of the chlorine gas in the vessel?
This problem requires us to substitute the moles of gas in the ideal gas law to mass over molar mass.
We can then isolate for the mass of chlorine gas in the vessel.
Chlorine is diatomic, so its molecular weight will be twice the atomic mass.
The temperature must be expressed in Kelvin.
Using these values, we can solve for the mass of chlorine gas in the vessel.
Example Question #11 : Ideal Gas Law
An ideal gas is initially at the following conditions:
The gas is then isothermally compressed to 15 atm.
What is the volume of the gas after compression? Round to the nearest liter.
The system is isothermal, which means the temperature is constant.
Example Question #12 : Ideal Gas Law
A sealed container containing 15L of oxygen gas, , with a pressure of 3atm at . How many grams of oxygen gas is present in the container? Assume ideal behavior of the gas.
is pressure, volume, moles, gas constant, temperature. Rearrange the equation, plug in the appropriate values and solve.
Example Question #13 : Ideal Gas Law
A sealed container containing 7L of an unknown gas, with a pressure of 6atm at . The amount of gas in the container is 68.8g. What is the molecular weight of the unknown gas present in the container? Assume ideal behavior of the gas.
is pressure, volume, moles, gas constant, temperature. Rearrange the equation, plug in the appropriate values and solve.
Since we start with 68.8g of the unknown gas, and we have 1.81mol, we can find the molecular weight.
Example Question #14 : Ideal Gas Law
A sealed container containing 4L of an unknown gas, with a pressure of 3atm at . The amount of gas in the container is 1.82g. What is the molecular weight of the unknown gas present in the container? Assume ideal behavior of the gas.
is pressure, volume, moles, gas constant, temperature. Rearrange the equation, plug in the appropriate values and solve.
Since we know we have 1.82g of the unknown gas, and we have 0.5mol, we can find the molecular weight by dividing grams by moles.
Example Question #11 : Ideal Gas Law
Match each gas law definition to the correct name of the person who is credited with discovering it: (a) The total pressure of a mixture of gases is equal to the sum of the pressures of each of the individual gases in the container. (b) The volume of a fixed amount of gas varies inversely with the pressure at constant temperature. (c) The temperature and volume of a gas at constant pressure are directly proportional. (d) The volume of two different gases at the same temperature and pressure is the same, and each sample contains the same number of gas molecules.
Avogadro, Boyle, Charles, Dalton
Dalton, Charles, Boyle, Avogadro
Avogadro, Charles, Boyle, Dalton
Dalton, Boyle, Charles, Avogadro
Dalton, Boyle, Charles, Avogadro
Dalton's Law of Partial Pressures states that the total pressure of a mixture of gases is equal to the sum of the pressures of each of the individual gases in the container. Boyle's Law states that the volume of a fixed amount of gas varies inversely with the pressure at constant temperature. Charles's Law states that the temperature and volume of a gas at constant pressure are directly proportional. Avogadro's Law can also be expressed by saying that one mole of any gas at standard temperature and pressure occupies 22.4L.
Example Question #12 : Ideal Gas Law
Each of the following compounds are contained in a closed container with a volume of 100mL. Which of the following will exert the most pressure?
40g H2
50g O2
60g CO2
46g N2
54g F2
40g H2
The pressure exerted is dependent on molar concentration only (not mass). As the containers are all the same volume, the container with the most moles will exert the most pressure. 60g of 44g/mole CO2 gives 1.4mol, 50g of O2 gives 1.4mol, 46g N2 gives 1.6mol, and 54g F2 gives 1.4mol, 40g H2 gives 40mol.
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