Discovery Task – Optional Extension
How to use the Chemistry Discovery List
You have been given a list of key statements which will help you make the link
between GCSE Chemistry and Advanced Level Chemistry.
The first week back in September will be very busy. However, your Chemistry
teacher will expect you to complete an Induction Task that assesses your
understanding of some of these statements. You will be expected to complete
this assignment in one week.
In the first term (and beyond) you will find that these topics are revisited at A’
Level and if you have a sound knowledge of these mathematical and chemical
concepts you are more likely to make a successful transition from Year 11 to
Year 12.
1
Discovery Task – Optional Extension
Moles and Molar Masses
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Know that the unit for the amount of a substance is the mole.
Know that the unit for molar mass is g/mol.
Understand that the term molar mass of a substance refers to its relative formula mass in grams.
Be able to calculate the molar mass of a substance from its formula (without brackets) using the
appropriate relative atomic masses.
Understand that mass is conserved during a chemical reaction.
Be able to interpret experimental results involving mass changes during chemical reactions.
Be able to use your understanding of conservation of mass to carry out very simple calculations:
o mass of gas or water lost during thermal decomposition
o mass of gas gained during reaction
o determine a reacting amount for a simple reaction given all the other reacting amounts.
Be able to calculate the molar mass of a substance from its formula (with brackets) using the appropriate
relative atomic masses.
Know and use the relationship between molar mass, number of moles and mass:
o number of moles = mass ÷ molar mass
o determine the number of moles of an element from the mass of that element
o determine the number of moles of a compound from the mass of that compound
o determine the masses of the different elements present in a given number of moles of a
compound.
Know that the relative atomic mass of an element is the average mass of an atom of the element
compared to the mass of 1/12th of an atom of carbon-12.
Given a set of reacting masses, be able to calculate further reacting amounts by simple ratio.
Be able to calculate mass of products and/or reactants using the mole concept from a given balanced
equation and the appropriate relative atomic masses.
Percentage composition and empirical formula
1. Be able to determine the mass of an element in a known mass of compound given the masses of the
other elements present.
2. Be able to calculate the molar mass of a substance from its formula (without brackets) using the
appropriate relative atomic masses.
3. Understand that an empirical formula gives the simplest whole number ratio of each type of atom in a
compound.
4. Be able to deduce the empirical formula of a compound given its chemical formula.
5. Be able to calculate the percentage by mass of an element in a compound given appropriate
experimental data about the mass of the element and the mass of the compound.
6. Know and use the relationship between molar mass, number of moles and mass:
o number of moles = mass ÷ molar mass.
7. Be able to determine the number of moles of an element from the mass of that element.
8. Be able to calculate empirical formula of a compound from the:
o percentage composition by mass
o mass of each element in a sample of the compound.
9. Be able to calculate the molar mass of a substance from its formula (with brackets) using the appropriate
relative atomic masses.
10. Be able to calculate the percentage by mass of an element in a compound given its formula and the
appropriate atomic masses.
2
Discovery Task – Optional Extension
Quantitative analysis
Know that concentration of solutions may be measured in g/dm3 (g per dm3).
Know that concentration of solutions may be measured in mol/dm3 (mol per dm3).
Know that volume is measured in dm3 or cm3.
Know that 1000 cm3 equals 1 dm3
Be able to describe how to dilute a concentrated solution.
Be able to explain the need for dilution in areas such as food preparation, medicine and baby milk:
o concentrated orange cordial needs to be diluted to make sure the taste is not too strong
o medicines may need to be diluted to avoid giving overdoses
o baby milk must be of the correct concentration so as not to harm the baby.
7. Be able to interpret information on food packaging about guideline daily amounts (GDA) for example:
o the smallest or largest amount of a particular substance.
8. Understand that the more concentrated a solution the more solute particles there are in a given volume
(the more crowded the solute particles).
9. Be able to convert volume in cm3 into dm3 or vice versa.
1.
2.
3.
4.
5.
6.
10. Know and use the relationship between the amount in moles, concentration in mol/dm3 and volume in
dm3:
o amount in moles = concentration × volume
o concentration = amount in moles ÷ volume
o volume = amount in moles ÷ concentration.
11. Be able to perform calculations involving concentration for simple dilutions of solutions eg how to dilute a
1.0 mol/dm3 solution into a 0.1 mol/dm3 solution or how to perform a 1 in 10 dilution.
12. Be able to interpret information on food packaging about guideline daily amounts (GDA) for example:
o percentage of GDA in a portion.
13. Interpret more complex food packaging information and its limitations for example:
o convert amounts of sodium to amounts of salt.
14. Be able to explain why the above conversion may be inaccurate, to include sodium ions coming from
other sources.
Titrations
1. Be able to describe and identify the apparatus used in an acid-base titration:
o burette
o conical flask
o pipette and pipette filler.
2. Be able to describe the procedure for carrying out a simple acid- base titration:
o acid in burette, alkali in conical flask (or vice versa)
o acid slowly added to alkali (or vice versa) until end point is reached
o end point detected by the sudden change in colour of an indicator.
3. Be able to explain why it is important to use a pipette filler when using a pipette in an acid-base titration.
4. Be able to calculate the titre given appropriate information from tables or diagrams.
5. Understand that the titre depends on the concentration of the acid or alkali.
6. Be able to calculate the concentration of an acid or alkali from titration results, limited to examples
involving a one to one molar ratio (acid:alkali).
7. Know and use the relationship between the amount in moles, concentration in mol/dm3 and volume in
dm3:
o amount in moles = concentration × volume
o concentration = amount in moles ÷ volume
o volume = amount in moles ÷ concentration.
3
Discovery Task – Optional Extension
Gas volumes
1. Be able to identify apparatus used to collect the volume of a gas volume produced in a reaction:
o gas syringe
o upturned measuring cylinder
o upturned burette.
2. Know that measurement of change of mass may be used to monitor the amount of gas made in a
reaction.
3. Be able to interpret data in table, graphical and written form about the volume of gas produced during the
course of a reaction for example:
o deduce total volume of gas produced
o deduce when the reaction has stopped
o deduce volume of gas at a particular time and vice versa
o compare rates of reaction using gradients of graphs.
4. Be able to describe an experimental method to measure the volume of gas produced in a reaction given
appropriate details about the reaction.
5. Be able to describe an experimental method to measure the mass of gas produced in a reaction given
appropriate details about the reaction.
6. Understand how the amount of product formed varies with the amount of limiting reactant used.
7. Know that the limiting reactant is the reactant not in excess that is all used up at the end of the reaction.
8. Be able to explain why a reaction stops in terms of the limiting reactant present given appropriate
qualitative information about the reaction.
9. Be able to explain in terms of reacting particles why the amount of product formed is directly proportional
to the amount of limiting reactant used.
10. Be able to calculate the volume of a known number of moles of gas given the molar gas volume of 24
dm3 at room temperature and pressure (rtp).
11. Be able to calculate the amount in moles of a volume of gas at rtp given the molar gas volume at rtp.
12. Be able to interpret data in table, graphical and written form about the volume of gas produced during the
course of a reaction (not major grid lines) for example:
o deduce total volume of gas produced
o deduce when the reaction has stopped
o deduce volume of gas at a particular time and vice versa
o deduce the volume of gas produced with different amounts of limiting reactant.
4
Induction Task - Compulsory
Transition to Advanced Level Chemistry
Mass
Convert the following into grams:
a)
b)
c)
d)
0.25 kg
15 kg
100 tonnes
2 tonnes
Volume
Convert the following into dm3:
a)
b)
c)
d)
100 cm3
25 cm3
50 m3
50000 cm3
What is a mole?
Atoms and molecules are very small – far too small to count individually!
It is important to know how much of something we have, but we count particles in MOLES because you get
simpler numbers
1 mole = 6.02 x 1023 particles
(6.02 x 1023 is known as Avogadro’s number)
a) If you have 2.5 x 1021 atoms of magnesium, how many moles do you have?
b) If you have 0.25 moles of carbon dioxide, how many molecules do you have?
5
Induction Task - Compulsory
How can you work out how many moles you have?
a) From a measurement of MASS:
You can find the number of moles of a substance if you are given its mass and you know its molar mass:
number of moles
n
=
mass/molar mass
=
m/mr
Mass MUST be measured in grams!
Molar mass has units of gmol-1
1. Calculate the number of moles
present in:
2. Calculate the mass of:
3. Calculate the molar mass of the
following substances:
a) 2.3 g of Na
a) 0.05 moles of Cl2
a) 0.015 moles, 0.42 g
b) 2.5 g of O2
b) 0.125 moles of KBr
b) 0.0125 moles, 0.50 g
c) 240 kg of CO2
c) 0.075 moles of Ca(OH)2
c) 0.55 moles, 88 g
d) 12.5 g of Al(OH)3
d) 250 moles of Fe2O3
d) 2.25 moles, 63 g
e) 5.2 g of PbO2
e) 0.02 moles of Al2(SO4)3
e) 0.00125 moles, 0.312 g
6
Induction Task - Compulsory
a) From a measurement of AQUEOUS VOLUME:
You can find the number of moles of a substance dissolved in water (aqueous) if you are given the volume
of solution and you know its molar concentration:
number of moles
=
aqueous volume
x
n
=
V
x
molar concentration
C
Aqueous volume MUST be measured in dm3!
concentration has units of moldm-3
If you know the molar mass of the substance, you can convert the molar concentration into a mass concentration:
Molar concentration (moldm-3)
x
1. Calculate the number of moles of
substance present in each of the
following solutions:
2. Calculate the molar concentration
and the mass concentration of the
following solutions:
3. Calculate the molar concentration
and the mass concentration of the
following solutions:
a) 25 cm3 of 0.1 moldm-3 HCl
a) 0.05 moles of HCl in 20 cm3
a) 35 g of NaCl in 100 cm3
b) 40 cm3 of 0.2 moldm-3 HNO3
b) 0.01 moles of NaOH in 25 cm3
b) 20 g of CuSO4 in 200 cm3
c) 10 cm3 of 1.5 moldm-3 NaCl
c) 0.002 moles of H2SO4 in 16.5 cm3
c) 5 g of HCl in 50 cm3
d) 5 cm3 of 0.5 moldm-3 AgNO3
d) 0.02 moles of CuSO4 in 200 cm3
d) 8 g of NaOH in 250 cm3
e) 50 cm3 of 0.1 moldm-3 H2SO4
e) 0.1 moles of NH3 in 50 cm3
e) 2.5 g of NH3 in 50 cm3
mr
mass concentration (gdm-3)
=
7
Induction Task - Compulsory
a)
From a measurement of GASEOUS VOLUME:
You can find the number of moles of a gas if you are given the volume of the gas:
number of moles
=
volume
/
24
n
=
V
/
24
24 dm3 is the volume occupied by 1 mole of any gas at room temperature and pressure
Volume MUST be measured in dm3!
1. Calculate the number of moles
present in:
2. Calculate the volume of gas
occupied by:
3. Calculate the mass of the following
gas samples:
a) 48 dm3 of O2
a) 0.05 moles of Cl2
a) 48 dm3 of O2
b) 1.2 dm3 of CO2
b) 0.25 moles of CO2
b) 1.2 dm3 of CO2
c) 200 cm3 of N2
c) 28 g of N2
c) 200 cm3 of N2
d) 100 dm3 of Cl2
d) 3.2 g of O2
d) 100 dm3 of Cl2
e) 60 cm3 of NO2
e) 20 g of NO2
e) 60 cm3 of NO2
8
Induction Task - Compulsory
Calculating Reacting Quantities from Chemical Equations
You perform these calculations in three steps:
-
calculate the number of moles of one of the substances (you will either be given the mass, or the
aqueous volume and the concentration, or the gaseous volume)
-
use the equation to work out the number of moles of the other substance
-
use one of the mole relationships to work out the quantity you need
1)
What mass of hydrogen is produced when 192 g of magnesium is reacted with hydrochloric acid?
Mg + 2 HCl  MgCl2 + H2
2)
(3)
What mass of oxygen is needed to react with 8.5 g of hydrogen sulphide (H2S)?
2 H2S + 3 O2  2 SO2 + 2 H2O
3)
(3)
What mass of potassium oxide is formed when 7.8 g of potassium is burned in oxygen?
4 K + O2  2 K2O
4)
(3)
What mass of oxygen is required to oxidise 10 g of ammonia to NO?
4 NH3 + 5 O2  4 NO + 6 H2O
(3)
9
Induction Task – Compulsory
5)
What mass of aluminium oxide is produced when 135 g of aluminium is burned in oxygen?
2 Al + 3 O2  Al2O3
6)
(3)
What mass of iodine is produced when 7.1 g of chlorine reacts with excess potassium iodide?
Cl2 + 2 KI  2 KCl + I2
7)
(3)
What volume of hydrogen is needed to react with 32 g of copper oxide?
CuO + H2  Cu + H2O
8)
(3)
What volume of oxygen is formed when 735 g of potassium chlorate decomposes?
2 KClO3  2 KCl + 3 O2
9)
(3)
What volume of hydrogen is produced when 195 g of potassium is added to water?
2 K + 2 H2O  2 KOH + H2
(3)
10