5 - Formulae, Equations and Amounts of Substance (A-Level Chemistry Edexcel 9CH0)

#5.1

know that the mole (mol) is the unit for amount of a substance

#5.2

be able to use the Avogadro constant, L, (6.02 × 10²³ mol^-1) in calculations

#5.3

know that the molar mass of a substance is the mass per mole of the substance in g mol^-1

#5.4

know what is meant by the terms ‘empirical formula’ and ‘molecular formula’

#5.5

be able to use experimental data to calculate

i) empirical formulae ii) molecular formulae including the use of pV = nRT for gases and volatile liquids

*Calculations of empirical formula may involve composition by mass or percentage composition by mass data. *

#5.6

be able to write balanced full and ionic equations, including state symbols, for chemical reactions

#5.7

be able to calculate amounts of substances (in mol) in reactions involving mass, volume of gas, volume of solution and concentration

*These calculations may involve reactants and/or products. *

#5.8

be able to calculate reacting masses from chemical equations, and vice versa, using the concepts of amount of substance and molar mass

#5.9

be able to calculate reacting volumes of gases from chemical equations, and viceversa, using the concepts of amount of substance

#5.10

be able to calculate reacting volumes of gases from chemical equations, and vice versa, using the concepts of molar volume of gases

#5.11

be able to calculate solution concentrations, in mol dm^-3 and g dm^-3, including simple acid-base titrations using a range of acids, alkalis and indicators

*The use of both phenolphthalein and methyl orange as indicators will be expected. *

#5.12

be able to:

i) calculate measurement uncertainties and measurement errors in experimental results ii) comment on sources of error in experimental procedures

#5.13

understand how to minimise the percentage error and percentage uncertainty in experiments involving measurements

#5.14

be able to calculate percentage yields and percentage atom economies using chemical equations and experimental results

$\text{Atom economy of a reaction} = \dfrac{\text{molar mass of the desired product}}{\text{sum of the molar masses of all products}} × 100\%$

#5.15

be able to relate ionic and full equations, with state symbols, to observations from simple test tube reactions, to include:

i) displacement reactions ii) reactions of acids iii) precipitation reactions

#5.16

understand risks and hazards in practical procedures and suggest appropriate precautions where necessary

#5P1

CORE PRACTICAL 1: Measure the molar volume of a gas

#5P2

CORE PRACTICAL 2: Prepare a standard solution from a solid acid and use it to find the concentration of a solution of sodium hydroxide

#5P3

CORE PRACTICAL 3: Find the concentration of a solution of hydrochloric acid

A-Level Chemistry Edexcel 9CH0

5: Formulae, Equations and Amounts of Substance