C2.3 Atomic structure, analysis and quantitative chemistry

The relative masses of atoms can be used to calculate how much to react and how much we can produce, because no atoms are gained or lost in chemical reactions. There are various methods used to analyse these substances.

Candidates should use their skills, knowledge and understanding to evaluate sustainable development issues relating the starting materials of an industrial process to the product yield and the energy requirements of the reactions involved.

Assessment and practical opportunities

investigating food colours using paper chromatography
working out the empirical formulae of copper oxide and magnesium oxide
calculating yields, for example magnesium burning to produce magnesium oxide or wire wool burning to produce iron oxide
there are opportunities in this section to build in the idea of instrumentation precision, eg for the collection of gases, the use of boiling tubes, gas jars or gas syringes
copper sulfate – hydration/dehydration
heating ammonium chloride in a test tube
adding alkali and acid alternately to bromine water or to potassium chromate solution
‘blue bottle’ reaction (RSC Classic Chemistry Experiments no. 83)
oscillating reaction (RSC Classic Chemistry Experiments no.140).

 


Quantitative chemistry - Balancing chemical equations Deriving empirical and molecular formulae The percentage of an element in a compound can be calculated from the relative mass of the element in the formula and the relative formula mass of the compound. The empirical formula of a compound can be calculated from the masses or percentages of the elements in a compound. Candidates should be able to calculate empirical formulae. Experiment to
Analysing substances - Elements and compounds can be detected and identified using instrumental methods. Instrumental methods are accurate, sensitive and rapid and are useful when the amount of a sample is very small. Paper Chromatography Chemical analysis can be used to identify additives in foods. Artificial colours can be detected and identified by paper chromatography. Knowledge of methods other than paper chromatography is not required, but questions may include
Atomic structure definitions - Mass number: The total number of protons and neutrons in an atom is called its mass number. Atomic number: the total number of protons (=electrons) in an atom. This number characterises the element type. Isotopes: Atoms of the same element can have different numbers of neutrons; these atoms are called isotopes of that element. Relative atomic mass (Ar): compares the mass of atoms of

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