Kinetic Theory & Ideal Gases (Edexcel International A Level Physics)

Natural gas produced from landfill consists of a mixture of methane and carbon dioxide gases.

At a temperature of 20.0°C and a pressure of 1.01 × 10⁵ Pa the volume occupied by 1 mole of carbon dioxide is 0.0241 m³.

Show that the number of molecules in 1 mole of carbon dioxide is about 6.0 × 10²³.

In a sample of natural gas, the r.m.s. velocity of the carbon dioxide molecules is 60.5% of the r.m.s. velocity of the methane molecules.

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The school apparatus shown is used to demonstrate a gas law.

Air is trapped in a glass tube of uniform cross-sectional area. A pump forces oil into the base of the glass tube. This forces the air into a smaller volume. The pressure of the trapped air is displayed on the pressure gauge.

The pressure of the trapped air increases when the air is forced into a smaller volume.

Explain why, using ideas of molecular motion.

The apparatus is used in a laboratory where the temperature is 293 K.

When the air occupies a volume of 2.43 × 10⁻³ m³ the reading on the pressure gauge is 1.05 × 10⁵ Pa.

Calculate the number of molecules of air trapped in the glass tube.

Number of molecules of air = ......................................