Amount of
substance
Learning outcomes
You should be able to:
 understand the Avogadro number and mole (of
particles)
 be able to carry out calculations involving quantities of
substances expressed in moles
 be able express solution concentrations in mol dm-3
 recall and understand the use of the ‘molar volume’
 recall and be able to use the ideal gas equation
 know how to balance equations
 know how to balance ionic equations
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WHAT IS A MOLE ?
The standard unit
of amount of a
substance
WHY ARE MOLES USED?
To make easier to weigh
substances
HOW BIG IS IT ?
6.022 x 1023
Ideal Gas Equation
Volume
Pressure
PV=nRT
No. of moles
R = 0.0821 atm L / mol K
R = 8.314 kPa L / mol K
Kelter, Carr, Scott, Chemistry A Wolrd of Choices 1999, page 366
Universal Gas Constant
Temperature
Practice Questions
Q1 How many molecules are there in one mole
of carbon dioxide molecules?
Q2 How many atoms are in there 0.500 moles of
carbon?
Q3 A student dissolves 0.100 moles of NaCl in
500 cm3 of water. Find the concentration of the
solution?
Q4 Write down the ideal gas equation.
SUMMARY – USING MOLES
for gases:
for solutions:
n = PV
RT
n = CV
use the ratios
in the equation
to find the number
of moles of other
species
n = mass
RMM
n = particles
NL
A
MOLES OF A SINGLE SUBSTANCE
1.Calculate the number of moles
2.Calculate the mass of substance
3.Calculate the relative molecular mass
REACTING MASS CALCULATIONS
To calculate the reacting mass there are 3 steps:
1. Write out the balanced equation;
2. Work out the Mr;
3. Apply the rule ‘divide to get one or multiply to get all’
WELL DONE!
Try some past paper questions