10 minutes maximum! Can you do it in 5?

1. The ideal gas equation is PV = nRT. In this formula, 'n' is ....

• A. the number of molecules in the gas.
• B. the number of moles of gas.
• C. the number of molecules per mole.
• D. the atomic mass number of the gas.

2. The element Helium has an atomic mass of 4 and a proton number of 2. How many moles are there in 20 g of Helium gas?

• A. 2
• B. 4
• C. 5
• D. 10

3. A student writes down three statements about the molecules in a gas:

• I : The molecules are much smaller than the space between molecules.
• II : The forces between the molecules are negligible.
• III. All collisions between molecules and the walls of the container are elastic.

Which of these statements are true for an ideal gas?

• A. I only.
• B. I and II only.
• C. II and III only.
• D. I , II and III.

4 - 6. The four graphs below show the relationship between some quantities for an ideal gas: Which of the graphs above shows the relationship between...

4. .. the pressure (y - axis) to the temperature in kelvin (x - axis), at constant volume and mass of gas.

5. .. the pressure (y - axis) to the volume (x - axis), at constant temperature and mass of gas.

6. .. the mean kinetic energy of molecules (y - axis) to the temperature in kelvin (x - axis).

7. A real gas behaves similarly to an ideal gas when the pressure and density of the gas are suitable. Which of these statements best describes these pressure and density conditions?

 Density Pressure A low low B low high C high low D high high

8&9. A sample of an ideal gas is trapped inside a container of volume V and at a temperature T. The pressure inside the container is P.

The value R is the ideal gas constant.

8. Which of these formulas gives the number of moles of gas inside the container? 9. The gas is compressed to half the volume, and the temperature increased to 2T. The mass of gas in the container remains the same. The new pressure in the container is now ...

• A. ½P
• B. P
• C. 2P
• D. 4P

10. Hydrogen gas H2 has a molar mass of 2 g. How many molecules are in 2 kg of H2 gas?

• A. 6 x 1020
• B. 6 x 1023
• C. 6 x 1026
• D. 6 x 1027