Category Archives: 1.2 Amount of substance

Mass spectrometry (AS and A2 analytical techniques)

This topic overlaps organic analysis for AS and A2. High resolution mass spectrometry can be used to determine the molecular formula of a compound from the accurate mass of the molecular ion. Understand that the fragmentation of a molecular ion: M+• → X+ + Y• gives rise to a characteristic relative abundance spectrum that may give information about the structure of

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Balanced equations and associated calculations

But, as total mass of products=total mass of reactants [Law of conservation of mass], then Assessment and practical opportunities • write balanced equations (full and ionic) for reactions studied • balance equations for unfamiliar reactions when reactants and products are specified. Students should be able to use balanced equations to determine: • masses • reacting volumes of gases • percentage yields •

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Empirical and molecular formula

Empirical formula is the simplest whole number ratio of atoms of each element in a compound. Molecular formula is the actual number of atoms of each element in a compound. The relationship between empirical formula and molecular formula. Assessment and practical activities Students should be able to: • calculate empirical formula from data giving composition by mass or percentage by mass • calculate molecular

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The mole and the Avogadro constant

The Avogadro constant as the number of particles in a mole. The mole as applied to electrons, atoms, molecules, ions, formulas and equations. The concentration of a substance in solution, measured in mol dm-3. [Students will not be expected to recall the value of the Avogadro constant] Assessment and practical skills Students should be able to carry out calculations: • using the Avogadro constant

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