Deducing an empirical formula experimentally: using moles
I can describe and carry out an experiment to determine the empirical formula of a simple compound.
Deducing an empirical formula experimentally: using moles
I can describe and carry out an experiment to determine the empirical formula of a simple compound.
These resources will be removed by end of Summer Term 2025.
Lesson details
Key learning points
- Small masses of a substance, including magnesium, can be easily heated in a crucible.
- The crucible needs to be opened periodically to allow air (i.e. oxygen) to enter the apparatus.
- Lifting a crucible lid too often or for too long may lead to loss of product (i.e. lower final mass recorded).
- Using practical data and conservation of mass, chemists can calculate unknown reactant masses.
- Reactant masses can determine the empirical formula of a substance, including the ionic molar ratio of a metal & oxygen.
Keywords
Empirical formula - A substance's empirical formula shows the simplest whole number ratio of atoms of each element in a compound.
Evaluate - To evaluate something is to make a judgement about it with respect to a particular purpose.
Mole - A mole of something is 6.02 × 10²³ of it. The mass of a mole of a substance is its relative mass expressed in grams.
Relative atomic mass - Relative atomic mass is the mean mass of an atom relative to 1/12th the mass of an atom of carbon–12.
Common misconception
Pupils think that simply ensuring a fair test will improve data collecting in a practical.
Evaluating a practical is an often overlooked skill. Challenge pupils to focus on the equipment chosen and/or the method followed to consider how better data might be collected.
Equipment
balance (ideally 2 d.p.) magnesium strips (~3 cm) crucible and li. Bunsen burner tripod + clay triangle heatproof mat tongs
Content guidance
- Risk assessment required - equipment
Supervision
Adult supervision required
Licence
This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).
Lesson video
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