The Gaseous State: Ideal & Real Gases & pV = nRT (CIE A Level Chemistry)

An experiment is conducted to calculate the M_r of an unknown gas of known mass. 

Measurements of pressure, volume and temperature are taken during the experiment.

Which conditions of temperature and pressure would give the most accurate value of M_r?

0.96 g of hydrogen gas is contained in a sealed vessel of volume of 7.0 × 10⁻³ m³ at a temperature of 303 K. 

Assume the gas behaves as an ideal gas. 

What is the pressure of the vessel?

A 5370 cm³ sample of oxygen is measured at a temperature of 60°C. The pressure measured was 103000 Pa. 

Assume the gas behaves as an ideal gas.

What is the mass of the sample of oxygen?

A sample of chlorine gas with a of mass 5.35 g has a volume of 1.247 × 10^-3 m³ at a pressure of 1.00 × 10⁵ Pa.

Assuming the gas acts as an ideal gas, what is the temperature of the gas?

A bubble travelled up from the sea bed to the surface. Just below the surface of the sea the bubble had a volume of 200 cm³ at a pressure of 101 kPa, the temperature at the surface is the same as the sea bed.

The pressure at the sea bed is 2020 kPa.

What is the volume of the bubble at the sea bed?

Sodium reacts with water in the equation below.

2Na (s) + 2H₂O (l) → 2NaOH (aq) + H₂ (g)

Which mass of sodium reacts with water to produce 960 cm³ of hydrogen gas under standard pressure and room temperature?

At 298 K and 101 kPa which compound is the only gas?

When a sample of a gas is compressed at room temperature from 101 kPa to 300 kPa, its volume changes from 50.0 cm³  to 17.5 cm³.

Which statement best describes why this happens?

What mass of a gas would occupy a volume of 3 dm³ at 25 ℃ and 1 atmosphere pressure? 

1 mol of a gas occupies 24 dm³ at 25 ℃ and 1 atmosphere pressure.

Real gases deviate from ideal behaviour. The extent to which they deviate depends on the identity of the gas.  

Plots of pV against p for three real gases W, X, Y and an ideal gas are shown below.

What are the identities of gases W, X, Y? 

Which expression gives the pressure exerted by 1.5 × 10^-2 mol of carbon dioxide in a container of volume 2 dm^-3 at 275 ℃?

A tube of volume 0.3 dm³ is filled with a gas at 27 ℃ and 101 kPa, the mass of the tube increases by 1.02 10^-3 kg. 

Assume the gas is obeying the ideal gas laws. 

What is the identity of the gas?

The volume of a sample of methane is measured at a temperature of 50 ℃ and a pressure of 102 kPa, The volume measured was 5.25 dm³. [R = 8. 314 J mol^-1 K^-1] 

What is the mass of the sample of methane, given to two significant figures?

2.0 g of a metallic element reacts with 599 cm³ of oxygen at 298 K and 1 atm pressure, to form an oxide which contains O^2– ions.

What could be the identity of the metal?

Use of the periodic table is relevant to this question.

The volume of a sample of ammonia was measured at a temperature of 60 °C and a pressure of 75 kPa. The volume measured was 5.27 × 10^–5 m³.

What is the mass of the sample of ammonia?

The gas laws can be summarised in the ideal gas equation below.

pV = nRT

When an evacuated tube of volume 560 cm³ is filled with gas at 340 K and 101 kPa, the mass of the tube increases by 0.8 g. Assume the gas behaves as an ideal gas. 

Which noble gas has been added to the tube?

The glass containers X and Y are connected by a closed valve.

X contains pure CO₂ gas at 25 °C and a pressure of 1 × 10⁵ Pa. Container Y has been evacuated prior to the experiment and has a volume three times bigger than container X. 

During the experiment, the valve is opened, and the temperature of the whole apparatus is raised to 160 °C.

What is the final pressure in the system?

0.84 g of a metallic element reacts completely with 5000 cm³ of oxygen at 441 K and 22 kPa pressure to form an oxide which contains O^2– ions.

What could be the identity of the metal?

Flask Q contains 4 dm³ of neon at 10 kPa pressure, and flask R contains 10 dm³ of helium at 5 kPa pressure.

If the flasks are connected at a constant temperature, what is the closest final pressure?

The atmospheric composition on four different planets is given in the table below.

The density of a gas can be defined as the mass of 1 dm³ of the gas measured at standard conditions. 

Which atmosphere is the most dense?