0 0 Moodle
Home Revision Notes Courses For Schools Blog My Account Cart
Moodle
OCR A Level Chemistry A – Module 2 Foundations in Chemistry

2.1.3
Amount of Substance

Section 2.1.3 covers the mole and the Avogadro constant, molar mass and molar gas volume, empirical and molecular formulae, hydrated salts, calculations with masses, gas volumes and solutions, the ideal gas equation, percentage yield and atom economy. These pages cover the mole, formulae and every calculation type; hydrated salts and measuring techniques follow with the supplementary set.

Exam Paper
Paper 1 & 2
H432/01 and H432/02
Specification Points
2.1.3 (a) – (j)
10 learning outcomes
Topic Parts
4 of 4 live
Atoms, Mole Calculations, Formulae, Solutions and Gases
Exam Board
OCR A
H432 (2015 onwards)

Revision Notes

Work through 2.1.3 in a structured sequence.

Foundations
Atoms, Elements
and Molecules
1

Atoms, Elements and Molecules

Atoms, elements, ions and molecules, relative masses, molar mass, the mole and the Avogadro constant (2.1.3 (a)).

Start revising
Calculations
Mole
Calculations
2

Mole Calculations

Comparing masses, calculations involving moles, reacting masses, percentage yield and atom economy (2.1.3 (e), (g), (h), (j)).

Start revising
Formulae
Empirical and
Molecular
3

Empirical and Molecular Formulae

Empirical formulae from composition by mass and molecular formulae from Mᵣ (2.1.3 (b), (c)).

Start revising
Gases and solutions
Solutions
and Gases
4

Calculations with Solutions and Gases

Molar gas volume, the ideal gas equation and concentrations of solutions (2.1.3 (a)(v), (e), (f)).

Start revising
Water of crystallisation
Hydrated
Salts
5

Hydrated Salts and Water of Crystallisation

Anhydrous and hydrated salts, and finding x in a hydrated salt from percentage composition or heating to constant mass (2.1.3 (d)).

Start revising
Apparatus
Measuring
Techniques
6

Measuring Mass, Volume and Gas Volume

Weighing by difference, pipettes, burettes and volumetric flasks, collecting gases, and percentage uncertainty (2.1.3 (i)).

Start revising
Specification Coverage

2.1.3 Amount of Substance – OCR A Level Chemistry A

The following OCR A learning outcomes state what candidates should be able to do. Wording is taken from the OCR A Level Chemistry A (H432) specification.

2.1.3 Amount of Substance

2.1.3(a)
Amount of substance and the mole
i
explanation and use of the term amount of substance
ii
explanation and use of the term mole (symbol ‘mol’), as the unit for amount of substance
iii
explanation and use of the term the Avogadro constant, NA (the number of particles per mole, 6.02 × 10^23 mol–1)
iv
explanation and use of the term molar mass (mass per mole, units g mol–1)
v
explanation and use of the term molar gas volume (gas volume per mole, units dm3 mol–1)
2.1.3(b)
Empirical and molecular formula
i
use of the term empirical formula (the simplest whole number ratio of atoms of each element present in a compound)
ii
use of the term molecular formula (the number and type of atoms of each element in a molecule)
2.1.3(c)
Calculating formulae
i
calculations of empirical formulae from composition by mass
ii
calculations of empirical formulae from percentage compositions by mass
iii
calculations of molecular formulae from composition by mass or percentage compositions by mass and relative molecular mass
2.1.3(d)
Hydrated salts
i
the term anhydrous
ii
the term hydrated
iii
the term water of crystallisation
iv
calculation of the formula of a hydrated salt from given percentage composition
v
calculation of the formula of a hydrated salt from given mass composition
vi
calculation of the formula of a hydrated salt based on experimental results
2.1.3(e)
Calculations using amount of substance
i
calculations, using amount of substance in mol, involving mass
ii
calculations, using amount of substance in mol, involving gas volume
iii
calculations, using amount of substance in mol, involving solution volume and concentration
2.1.3(f)
The ideal gas equation
the ideal gas equation: pV = nRT
2.1.3(g)
Stoichiometric relationships
use of stoichiometric relationships in calculations
2.1.3(h)
Percentage yield and atom economy
i
calculations to determine the percentage yield of a reaction or related quantities
ii
calculations to determine the atom economy of a reaction
2.1.3(i)
Techniques and procedures
i
the techniques and procedures required during experiments requiring the measurement of mass
ii
the techniques and procedures required during experiments requiring the measurement of volumes of solutions
iii
the techniques and procedures required during experiments requiring the measurement of gas volumes
2.1.3(j)
Sustainability and atom economy
the benefits for sustainability of developing chemical processes with a high atom economy