Science: Gas Laws: Boyles, Charles, and Ideal Gas
Relating pressure, volume, temperature, and moles in gases
Science: Gas Laws: Boyles, Charles, and Ideal Gas
Relating pressure, volume, temperature, and moles in gases
Chemistry - Grade 9-12
- 1
A gas sample has a volume of 4.0 L at a pressure of 1.5 atm. If the temperature stays constant and the pressure increases to 3.0 atm, what is the new volume?
For Boyle's law, pressure and volume change while temperature stays constant.
Using Boyle's law, P1V1 = P2V2. Substituting values gives (1.5 atm)(4.0 L) = (3.0 atm)(V2). Solving gives V2 = 2.0 L. The new volume is 2.0 L. - 2
A balloon has a volume of 2.5 L at 300 K. If the pressure remains constant and the temperature increases to 360 K, what is the new volume?
Using Charles's law, V1/T1 = V2/T2. Substituting values gives 2.5 L/300 K = V2/360 K. Solving gives V2 = 3.0 L. The new volume is 3.0 L. - 3
A container holds 1.0 mol of gas at 2.0 atm and 273 K. If the container volume is 11.2 L, does this data agree with the ideal gas law? Use R = 0.0821 L-atm/mol-K.
Compare the value of PV with the value of nRT.
Using the ideal gas law, PV = nRT. Calculate nRT = (1.0 mol)(0.0821 L-atm/mol-K)(273 K) = 22.4 L-atm. Calculate PV = (2.0 atm)(11.2 L) = 22.4 L-atm. Since both sides are equal, the data agrees with the ideal gas law. - 4
A gas occupies 750 mL at 25 degrees C. If the pressure stays constant and the gas is cooled to 0 degrees C, what is the new volume? Express your answer in milliliters.
First convert temperatures to kelvin. The initial temperature is 298 K and the final temperature is 273 K. Using Charles's law, V1/T1 = V2/T2. Substituting values gives 750 mL/298 K = V2/273 K. Solving gives V2 about 687 mL. The new volume is about 687 mL. - 5
A syringe contains 30.0 mL of air at 1.00 atm. The plunger is pushed until the volume is 12.0 mL at constant temperature. What is the new pressure?
When volume decreases at constant temperature, pressure increases.
Using Boyle's law, P1V1 = P2V2. Substituting values gives (1.00 atm)(30.0 mL) = (P2)(12.0 mL). Solving gives P2 = 2.50 atm. The new pressure is 2.50 atm. - 6
A gas has a volume of 5.00 L, a pressure of 1.20 atm, and a temperature of 350 K. How many moles of gas are present? Use R = 0.0821 L-atm/mol-K.
Using the ideal gas law, n = PV/RT. Substitute the values: n = (1.20 atm)(5.00 L) / [(0.0821 L-atm/mol-K)(350 K)]. This gives n about 0.209 mol. There are about 0.209 mol of gas present. - 7
A gas sample occupies 9.0 L at 0.80 atm. If the temperature remains constant, what pressure is needed to compress the gas to 6.0 L?
Set up the proportion so pressure and volume stay inversely related.
Using Boyle's law, P1V1 = P2V2. Substituting values gives (0.80 atm)(9.0 L) = (P2)(6.0 L). Solving gives P2 = 1.2 atm. The required pressure is 1.2 atm. - 8
A gas has a volume of 1.80 L at 250 K. At constant pressure, what temperature in kelvin is needed for the volume to increase to 2.16 L?
Using Charles's law, V1/T1 = V2/T2. Substituting values gives 1.80 L/250 K = 2.16 L/T2. Solving gives T2 = 300 K. The required temperature is 300 K. - 9
What is the pressure of 0.500 mol of a gas in a 10.0 L container at 300 K? Use R = 0.0821 L-atm/mol-K.
Solve the ideal gas law for pressure before substituting values.
Using the ideal gas law, P = nRT/V. Substitute the values: P = (0.500 mol)(0.0821 L-atm/mol-K)(300 K) / 10.0 L. This gives P about 1.23 atm. The pressure is about 1.23 atm. - 10
Explain in words the main difference between Boyle's law and Charles's law.
Boyle's law describes the relationship between pressure and volume when temperature is constant. Charles's law describes the relationship between volume and temperature when pressure is constant. - 11
A sealed flask contains gas at 2.0 L, 1.0 atm, and 300 K. If the amount of gas is 0.0812 mol, does this approximately satisfy PV = nRT? Use R = 0.0821 L-atm/mol-K.
Small differences can occur from rounding, so compare the values closely.
Calculate PV first: (1.0 atm)(2.0 L) = 2.0 L-atm. Then calculate nRT: (0.0812 mol)(0.0821 L-atm/mol-K)(300 K) about 2.00 L-atm. Since the values are approximately equal, the flask data does satisfy the ideal gas law. - 12
A student says gas temperatures can be used in degrees Celsius directly in Charles's law calculations. Is the student correct? Explain.
The student is not correct. Charles's law requires absolute temperature, so temperatures must be converted to kelvin before calculating. Using degrees Celsius directly can give incorrect ratios and incorrect answers.