Gas volumes and the ideal gas equationEdexcel International A Level Chemistry: Flashcards

What these 13 flashcards ask

What is the molar volume of a gas at rtp?
What does rtp stand for and what are its values?
State the ideal gas equation with the units of each term.
Convert 85.0 cm3 to m3.
Convert 2.50 dm3 to m3.
Convert 101 kPa to Pa.
How do you convert from °C to K?
Rearrange pV = nRT to give the amount of gas.
How do you find molar mass from gas data?
What happens to the pressure of a fixed amount of gas at constant volume if the kelvin temperature doubles?
In Core Practical 1, why is excess acid used?
In Core Practical 1, how is the molar volume calculated?
Give two reasons why the volume of gas in Core Practical 1 might be too low.

Exam questions on Gas volumes and the ideal gas equation

A student reacts 0.120 g of magnesium ribbon with an excess of dilute hydrochloric acid and collects the hydrogen in a gas syringe at room temperature and pressure (rtp). The molar volume of a gas at rtp is 24.0 dm³ mol⁻¹. The relative atomic mass of magnesium is 24.3.
The student collects only 108 cm³ of hydrogen. Suggest two reasons why the measured volume is less than the calculated volume.2 marks
A gas cylinder of fixed volume 2.50 dm³ contains 4.00 g of methane, CH₄ (molar mass 16.0 g mol⁻¹), at 300 K. Take R = 8.31 J K⁻¹ mol⁻¹ and the molar volume at rtp as 24.0 dm³ mol⁻¹.
Calculate the volume the methane would occupy at rtp and use this to state whether the gas in the cylinder is at a higher or lower pressure than atmospheric pressure.2 marks
A volatile liquid X is one of propanone (C₃H₆O), diethyl ether (C₄H₁₀O) or hexane (C₆H₁₄). A sample of mass 0.205 g is vaporised completely in a gas syringe and occupies 85.0 cm³ at 373 K and a pressure of 101 kPa. Take R = 8.31 J K⁻¹ mol⁻¹. Relative atomic masses: H = 1.0, C = 12.0, O = 16.0.
Calculate the amount, in mol, of X in the gas syringe.3 marks

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).