A-Level Physics-Ideal Gas

What is meant by an ideal gas?

• A gas that obeys Charle's law (V1/T1 = V2/T2) at any volume (V) and temperature (T, in K)

• A gas that obeys Boyle's law (P1/V1 = P2/V2) at any pressure (P) and volume (V)

• A gas that obeys the ideal gas law (PV/T = constant) at any pressure (P), temperature (T, in °C) and volume (V)

• A gas that obeys the ideal gas law (PV/T = constant) at any pressure (P), temperature (T, in K) and volume (V)

What conditions are required for the equation (PV/T = constant) to be valid?

I - Gas must be an ideal gas

II - Low temperature

III - High pressure

IV - Fixed mass of gas

• I only

• I, II & III

• I & IV

• II & III

State & explain the first law of thermodynamics.

• ∆U = q + w ; energy transferred to system by heating

  plus work done on the system

• ∆U = q + w ; energy transferred out of system by heating

  plus work done on the system

• ∆U = q + w ; energy transferred to system by heating

  plus work done by the system

• ∆U = q + w ; energy transferred out of system by heating

  plus work done by the system

Which of the following basic assumptions of the kinetic theory of gases is false?

• Volume of atoms is negligible compared to volume of containing vessel

• Atoms does not behave as elastic identical spheres

• No forces of attraction or repulsion between atoms

• Atoms are in continuous random motion

A balloon is filled with helium gas at a pressure of 1.1 x 10^5Pa & a temperature of 25°C.

The balloon has a volume of 6.5 x 10^4cm^3. Helium may be assumed to be an ideal gas.

Determine the number of gas atoms in the balloon.

• 1.7 x 10^24

• 1.78 x 10^24

• 1.7 x 10^30

• 2.1 x 10^25

What is meant by the Avogadro constant NA?

• Number of atoms of carbon-12

  in 0.012g of carbon-12

• Number of atoms of carbon-12

  in 0.12kg of carbon-12

• Number of atoms of carbon-12

  in 0.012kg of carbon-12

• Number of atoms of carbon-12

  in 0.12g of carbon-12

The molecules of an ideal gas have a root-mean square (r.m.s.) speed of 520ms^-1 at a temperature of 27°C. Calculate the r.m.s. speed of the molecules at a temperature of 100°C.

• 579ms^-1

• 1930ms^-1

• 1000ms^-1

• 580ms^-1

A gas cylinder of volume 2.1 x 10^4cm^3 contains helium-4 gas at pressure 6.1 x 10^5Pa & temperature 12°C. Helium-4 may be assumed to be an ideal gas.

Determine the amount, in mol, for the helium gas.

• 5.4 x 10^6mol

• 5.4mol

• 1.3 x 10^2mol

• 1.3 x 10^8mol

What is meant by the internal energy of a system?

• Sum of kinetic and potential energies of the molecules

• Sum of the random distribution of thermal and potential energies of the molecules

• Sum of the random distribution of kinetic and potential energies of the molecules

• Sum of the distribution of kinetic and potential energies of the random molecules

Explain why, for an ideal gas, the internal energy is equal to the total kinetic energy of the molecules of the gas?

• For an ideal gas, there is no intermolecular forces

  so no potential energy & thus only kinetic

• For an ideal gas, there is no forces of attraction or repulsion between the atoms & thus only kinetic

• For an ideal gas, the atoms behave as elastic identical spheres & thus only kinetic

• For an ideal gas, the atoms are in continuous random motion & thus only kinetic