A-Level Chemistry OCR A H432

explanation and use of the terms:

(i) amount of substance (ii) mole (symbol ‘mol’), as the unit for amount of substance (iii) the Avogadro constant, N_A (the number of particles per mole, 6.02 × 10²³ mol^–1) (iv) molar mass (mass per mole, units g mol^–1), (v) molar gas volume (gas volume per mole, units dm³ mol^–1)

Amount of substance will be used in exams using the formula of the substance, e.g. amount of NaCl; amount of O₂. The value for N_A and the molar gas volume at RTP are provided on the Data Sheet.

use of the terms:

(i) empirical formula (the simplest whole number ratio of atoms of each element present in a compound) (ii) molecular formula (the number and type of atoms of each element in a molecule)

Definitions not required.

calculations of empirical and molecular formulae, from composition by mass or percentage compositions by mass and relative molecular mass

*To include calculating empirical formulae from elemental analysis data (see also 6.3.2e). *

the terms anhydrous, hydrated and water of crystallisation and calculation of the formula of a hydrated salt from given percentage composition, mass composition or based on experimental results

PAG1

calculations, using amount of substance in mol, involving:

(i) mass (ii) gas volume (iii) solution volume and concentration

Learners will be expected to express concentration in mol dm^–3 and g dm^–3.

the ideal gas equation:

$pV = nRT$

The value for R is provided on the Data Sheet. Learners will be expected to express quantities in SI units.

use of stoichiometric relationships in calculations

calculations to determine:

(i) the percentage yield of a reaction or related quantities (ii) the atom economy of a reaction

the techniques and procedures required during experiments requiring the measurement of mass, volumes of solutions and gas volumes

PAG1

the benefits for sustainability of developing chemical processes with a high atom economy.