A laboratory technician studies samples of methane, CH₄, and helium.
The Avogadro constant is 6.02 × 10²³.
| Element | H | C |
|---|---|---|
| Relative atomic mass, Aᵣ | 1.0 | 12.0 |
A methane sample has a mass of 2.40 g.
Calculate the total number of atoms in the sample.
Give your answer in standard form to 3 significant figures.
Total number of atoms = ......
A different methane sample contains 9.03 × 10²² hydrogen atoms.
Calculate the mass of methane in this sample.
Mass of methane = ...... g
A technician says:
“0.200 mol of methane contains the same total number of atoms as 1.00 mol of helium.”
Evaluate the technician’s statement.
134 exam-style questions on OCR GCSE Chemistry 3.1 Introducing chemical reactions, covering 3.1.1 Writing formulae and balanced chemical equations, 3.1.2 Formulae of compounds from ions, and state symbols, 3.1.3 Conservation of mass and observed changes in mass, 3.1.4 Half equations and balanced ionic equations, 3.1.5 The mole and the Avogadro constant, and 3.1.6 Stoichiometry, limiting reactants and reacting masses. Each one has a worked solution and a mark scheme showing where the marks go.