Gases Laws

Which constant correctly describes the amount of substance in moles?

• PV = constant

• N_A = constant

• P/T= constant

• k = R/N_A = constant

The model of the kinetic theory of gases has four main assumptions. Which one of the following assumptions has a mistake?

• Negligible forces between particles except during collision

• Particles (atoms or molecules) occupy negligible volume compared to the volume of gas

• All collisions are inelastic and the time of the collisions is negligible compared to the time between collisions

• Large number of molecules in random, rapid motion

Tags

NGSS.HS-PS3-2

NGSS.HS-PS3-4

Which equation does not correctly describe the relationship between pV where p is the pressure and V is the volume of a gas?

• pV = NkT

• pV = nRT

• pV = R/N_A

• pV = 1/3 NmC ²

How many atoms are there in 0.25 moles of N₂ gas?

• 3.76 × 10²² atoms

• 2.41 × 10²⁴ atoms

• 7.53 × 10²² atoms

• 4.82 × 10²⁴ atoms

An extremely small sample of oxygen gas contains just four molecules moving in one line. Their velocities are 0.550 km s⁻¹, −0.500 km s⁻¹, −0.050 km s⁻¹. Calculate the r.m.s speed of these molecules in m s⁻¹.

• 0.185 m s⁻¹

• 366 m s⁻¹

• 185 000 m s⁻¹

• 430 m s⁻¹

Calculate the average speed of a nitrogen molecule at a temperature of 600 K if the mass of a nitrogen molecule is 4.7 × 10⁻²⁶ kg.

• 528 000 m s⁻¹

• 1.37 × 10⁻³ m s⁻¹

• 726 m s⁻¹

• 1.89 × 10⁻⁶ m s⁻¹

Tags

NGSS.HS-PS2-1

Neon is a monotomic gas with a molecular mass of 20.0 g. It is kept in a container of volume 7.00 m³ at a pressure of 3.90 × 10⁵ Pa and a temperature of 70.0 °C. Calculate the number of moles of neon in the container.

• 4690 moles

• 1.04 × 10⁻³ moles

• 958 moles

• 2.13 × 10⁻⁴ moles

At the top of Mount Everest the temperature is −23 °C and the air pressure is 3.3 × 10⁴ Pa. At sea level the temperature is 27 °C, the air pressure is 1.0 × 10⁵ Pa and the density of air is 1.2 kg m⁻³. Calculate the density of air at the top of Mount Everest.

• 3.0 kg m⁻³

• 3.1 kg m⁻³

• 0.48 kg m⁻³

• 0.46 kg m⁻³

Tags

NGSS.MS-ESS2-5

A bicycle tyre contains air at 20 °C. The volume of the tyre is 3.4 × 10⁻⁴ m³. The pressure in the tyre is 4.4 × 10⁵ Pa. To improve performance the pressure is increased to 6.9 × 10⁵ Pa. Calculate the mass of air that must be pumped into the tyre. Molecular mass of air 0.029 kg mol⁻¹.

• 0.03 kg

• 1.0 × 10⁻³ kg

• 2.8 × 10⁻³ kg

• 6.1 × 10²⁰ kg

In the derivation of the equation pV = 1/3Nmc² by considering how the movement of atoms or molecules of gas inside a sealed box gives rise to pressure, which explanation correctly explains the origin of the 1/3 term in the equation?

• On average, because of the random motion of the gas particles, about 1/3 of the particles will be moving between the two opposite faces of the container.

• There are three faces of the container.

• On average, there is 1/3 of a mole of gas particles in the container.

• On average, only 1/3 of the particles are moving at any one time.