Ideal gases

Which statement correctly defines internal energy?

• The sum of solar and wind energies of molecules in random motion.

• The sum of thermal and nuclear energies of molecules in random motion.

• The sum of kinetic and potential energies of molecules in random motion.

• The sum of useful and useless energies of molecules in random motion.

Which of the following is the ideal gas equation?

• pV = nRT

• pT = nRV

• pR = nRV

• pn = VRT

How many atoms are there in a mole of helium gas?

• 6.02 × 10¹³

• 6.02 × 10²³

• 1.20 × 10¹⁴

• 1.20 × 10²⁴

Which assumptions are made in the kinetic theory of gases?

• No forces between molecules.

• Volume of molecules is negligible.

• Molecules move in sync all the time.

• Molecules collide inelastically with each other.

A bar of gold has a mass of 1.00 kg. Calculate the number of moles of gold in the bar. (Relative atomic mass of gold = 197.)

• 1.97 × 10⁻³ mol

• 0.197 mol

• 5.08 mol

• 5.08 × 10⁻³ mol

In the equation
 $pV=\frac{1}{3}Nm<c^2>$ 

what is the origin of the factor  $\frac{1}{3}$  ?

• molecules move in 1-dimensional space
  

• molecules move in 2-dimensional space

• molecules move in 3-dimensional space

• molecules move in 4-dimensional space

What is the graph we'll get if we plot mean kinetic energy  $E_k$ of a molecule of an ideal gas against thermodynamic temperature $T$ ?

• straight line with positive gradient
  

• straight line with negative gradient
  

• quadratic curve
  

• circle

The following gases are at the same temperature. Which molecule will have the slowest r.m.s. speed?

• hydrogen

• carbon dioxide

• oxygen

• helium