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Regents Chemistry Practice By Topic Multiple Choice Questions And Solutions: Gases

June 2023


15 At STP, which property would be the same for 1.0 liter of helium and 1.0 liter of argon?

(1) boiling point

(2) density (3) mass (4) number of atoms


Solution: STP stands for standard temperature and pressure. When temperature, pressure, and volume (1L) is equal for two gases, the number of moles and atoms are equal as well. This is due to the ideal gas law (PV=nRT)

Answer: 4


August 2022


9. According to the kinetic molecular theory, which statement explains why an ideal gas can be compressed to a smaller volume?


(1) The motion of the gas particles is circular and orderly.

(2) The force of attraction between the gas particles is strong.

(3) As the gas particles collide, the total energy of the system decreases.

(4) The gas particles are separated by great distances relative to their size.


Solution: Kinetic molecular theory has the following statements which need to be memorized:

  1. Gas particles have negligible volume.

  2. The gas particles are in continuous random motion and move in straight lines.

  3. No forces of attraction or repulsion are considered to exist between the particles.

  4. Collisions of gas particles may transfer energy from one particle to another, but the total kinetic energy remains the same.

Answer: 4


20. Under which conditions of temperature and pressure does a sample of propane behave least like an ideal gas?


(1) 250. K and 1.0 atm

(2) 250. K and 5.0 atm

(3) 500. K and 1.0 atm

(4) 500. K and 5.0 atm


Solution: A sample of gas behaves MOST like an ideal gas under high temperature and low pressure. The question is asking us for conditions for gas to behave LEAST like an ideal gas which would be low temperature and high pressure.

Answer: 2



June 2022


16 Under which conditions of pressure and temperature is a real gas most like an ideal gas?

(1) low pressure and low temperature

(2) low pressure and high temperature

(3) high pressure and low temperature

(4) high pressure and high temperature


Solution:: A real gas behaves most like an ideal gas under high temperature and low pressure. This question is commonly encountered on the chemistry regents exam and this fact needs to be memorized.

Answer: 2


17 Which sample of argon gas has the same number of atoms as a 100.-milliliter sample of helium gas at 1.0 atm and 300. K?

(1) 50. mL at 1.0 atm and 300. K

(2) 50. mL at 0.5 atm and 300. K

(3) 100. mL at 0.5 atm and 300. K

(4) 100. mL at 1.0 atm and 300. K


Solution: When the temperature, pressure and volume is the same, the number of moles will be the same too according to the ideal gas law: PV=nRT

Answer: 4


January 2020


12 Which statement describes the particles of an ideal gas, based on the kinetic molecular theory?

(1) There are attractive forces between the particles.

(2) The particles move in circular paths.

(3) The collisions between the particles reduce the total energy of the gas.

(4) The volume of the gas particles is negligible compared with the total volume of the gas.


Solution: Kinetic molecular theory has the following statements which need to be memorized:

  1. Gas particles have negligible volume.

  2. Gas particles are in continuous random motion and move in straight lines.

  3. No forces of attraction or repulsion are considered to exist between the particles.

  4. Collisions of gas particles may transfer energy from one particle to another, but the total kinetic energy remains the same.

Answer: 4


41 The table below shows the volume and 44 temperature of four different gas samples at 100. kPa.



Which two gas samples contain equal numbers of atoms? (1) helium and neon

(2) helium and argon

(3) neon and argon

(4) neon and krypton


Solution: The two gases with the same volume, pressure and temperature will have the number of atoms.

Answer: 2


August 2019


18 According to the kinetic molecular theory, which statement describes the particles in a sample of an ideal gas?

(1) The particles are constantly moving in circular paths.

(2) The particles collide, decreasing the total energy of the system.

(3) The particles have attractive forces between them.

(4) The particles are considered to have negligible volume.

Solution: Kinetic molecular theory has the following statements which need to be memorized:

  1. Gas particles have negligible volume.

  2. Gas particles are in continuous random motion and move in straight lines.

  3. No forces of attraction or repulsion are considered to exist between the particles.

  4. Collisions of gas particles may transfer energy from one particle to another, but the total kinetic energy remains the same.

Answer: 4


19 Which sample of matter has the greatest distance between molecules at STP? (1) N2(g)

(3) C6H14(l)

(2) NH3(aq)

(4) C6H12O6(s)


Solution: Gases(g) have the greatest distance between molecules. Aq stands for aqueous (dissolved in water). L stands for liquid. S stands for solid.

Answer: 1


37 Which particle diagram represents a sample of oxygen gas at STP?



Solution: Oxygen is a diatomic element. This means we need to see a molecule that consists of two oxygen atoms. This eliminates choices 1 and 2. We are also looking for a gas phase where molecules are spread out. Choice 3 represents a liquid since molecules are close to one another.

Answer: 4


38 At which temperature and pressure will a sample of neon gas behave most like an ideal gas? (1) 300. K and 2.0 atm

(2) 300. K and 4.0 atm

(3) 500. K and 2.0 atm

(4) 500. K and 4.0 atm


Solution: A real gas behaves most like ideal gas at high temperature and low pressure.

Answer: 3


40 The volumes of four samples of gaseous compounds at 298 K and 101.3 kPa are shown in the table below.

Which two samples contain the same number of molecules?


(1) 1 and 2

(2) 1 and 3

(3) 2 and 3

(4) 2 and 4


Solution: Gases with the same pressure, temperature and volume have the same number of molecules.

Answer:2


June 2019


16 Which statement describes the particles of an ideal gas, based on the kinetic molecular theory?


(1) The volume of the particles is considered negligible.

(2) The force of attraction between the particles is strong.

(3) The particles are closely packed in a regular, repeating pattern.

(4) The particles are separated by small distances, relative to their size.


Solution: One of the statements of kinetic molecular theory is that the volume of particles of ideal gas is negligible ( we assume they have no volume).

Answer: choice 1


40 Which particle model diagram represents xenon at STP?


Solution: Xenon is a noble gas and we are looking for a gas particle diagram. Gas particles are far apart from one another, eliminating choice 3 and 4. Furthermore, xenon is not a diatomic gas, eliminating choice 2. Answer: Choice 1


January 2019


18 At STP, which gas sample has the same number of molecules as 2.0 liters of CH4(g) at STP? (1) 1.0 liter of C2H6(g)

(2) 2.0 liters of O2(g)

(3) 5.0 liters of N2(g)

(4) 6.0 liters of CO2(g)


Solution: Gases with the same pressure, temperature and volume have the same number of molecules

Answer: 2


40 A rigid cylinder with a movable piston contains a sample of hydrogen gas. At 330. K, this sample has a pressure of 150.kPa and a volume of 3.50L. What is the volume of this sample at STP? (1) 0.233 L

(2) 1.96 L

(3) 4.29 L

(4) 6.26 L


Solution: Table T on the Reference Table has an equation for the Combined Gas Law.

It is P1V1/T1= P2V2/T2

Also, STP stands for standard temperature and pressure which can be found in Table A. Standard pressure is 101.3 kPa and standard temperature is 273 K. Let's now write out all the given.

P1=150.kPa P2=101.3 kPa

V1=3.50L. V2=?

T1= 330. K T2=273 K

All there is left to do is plug these numbers into the formula and solve for V2.

Answer: 3


August 2018


6 At which temperature and pressure would a sample of helium behave most like an ideal gas? (1) 75 K and 500. kPa

(2) 150. K and 500. kPa

(3) 300. K and 50. kPa

(4) 600. K and 50. kPa

Solution:A real gas behaves most like ideal gas at high temperature and low pressure.

Answer: 4


18 Which sample at STP has the same number of atoms as 18 liters of Ne(g) at STP? (1) 18 moles of Ar(g) (2) 18 liters of Ar(g) (3) 18 grams of H2O(g) (4) 18 milliliters of H2O(g)


Solution:Gases with the same pressure, temperature and volume have the same number of molecules. The question has 18 liters of Ne in the given. We are looking for an answer choice with the same volume, 18 liters.

Answer: 2


42 A sample of a gas in a rigid cylinder with a movable piston has a volume of 11.2 liters at STP. What is the volume of this gas at 202.6kPa and 300. K?

(1) 5.10 L

(2) 6.15 L (3) 22.4 L

(4) 24.6 L


Solution:Table T on the Reference Table has an equation for the Combined Gas Law.

It is P1V1/T1= P2V2/T2

Also, STP stands for standard temperature and pressure which can be found in Table A. Standard pressure is 101.3 kPa and standard temperature is 273 K. Let's now write out all the given.

P1=101.3 kPa P2=202.6kPa

V1=11.2L. V2=?

T1= 273 K T2=300. K

All there is left to do is plug these numbers into the formula and solve for V2.

Answer: 2


January 2018


15 The kinetic molecular theory states that all particles of an ideal gas are

(1) colliding without transferring energy

(2) in random, constant, straight-line motion

(3) arranged in a regular geometric pattern

(4) separated by small distances relative to their size


Solution: Kinetic molecular theory has the following statements which need to be memorized:

  1. Gas particles have negligible volume.

  2. Gas particles are in continuous random motion and move in straight lines.

  3. No forces of attraction or repulsion are considered to exist between the particles.

  4. Collisions of gas particles may transfer energy from one particle to another, but the total kinetic energy remains the same.

Answer: 2


16 Which sample of gas at STP has the same number of molecules as 6 liters of Cl2(g) at STP? (1) 3 liters of O2(g)

(2) 6 liters of N2(g)

(3) 3 moles of O2(g)

(4) 6 moles of N2(g)


Solution: Gases with the same pressure, temperature and volume have the same number of molecules. We see 6 liters of Cl2 in the given and are looking for another gas with the same volume.

Answer:2


June 2018

16 Which phrase describes the motion and attractive forces of ideal gas particles? (1) random straight-line motion and no attractive forces (2) random straight-line motion and strong attractive forces (3) random curved-line motion and no attractive forces (4) random curved-line motion and strong attractive forces


Solution: According to Kinetic molecular theory ideal gas particles

  1. Gas particles have negligible volume.

  2. Gas particles are in continuous random motion and move in straight lines.

  3. No forces of attraction or repulsion are considered to exist between the particles.

  4. Collisions of gas particles may transfer energy from one particle to another, but the total kinetic energy remains the same.

Answer: 1


43 The table below shows data for the temperature, pressure, and volume of four gas samples


Which two gas samples contain the same number of molecules? (1) I and II

(2) I and III (3) II and III

(4) II and IV


Solution:Gases with the same pressure, temperature and volume have the same number of molecules.

Answer: 4


June 2017


17 Compared to a sample of helium at STP, the same sample of helium at a higher temperature and a lower pressure (1) condenses to a liquid (2) is more soluble in water (3) forms diatomic molecules (4) behaves more like an ideal gas


Solution: Real gases behave most like ideal gases at high temperature and low pressure.

Answer: 4



19 At STP, which gaseous sample has the same number of molecules as 3.0 liters of N2(g)?

(1) 6.0 L of F2(g)

(2) 4.5 L of N2(g) (3) 3.0 L of H2(g)

(4) 1.5 L of Cl2(g)


Solution: Gases with the same pressure, temperature and volume have the same number of molecules.

Answer:3


50 Which graph shows the relationship between pressure and Kelvin temperature for an ideal gas at constant volume?



Solution: Pressure and temperature are directly proportional. We know this from the ideal gas law PV=nRT. If two terms (such as P and V) are on the same side, they are inversely proportional. If two terms are on opposite sides such as P and T, they are directly proportional. Directly proportional means that as the temperature increases, pressure increases as well.

Answer: 1


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