Chemistry Revision
Session 4
Just to check from last week
Identify the colours of
Chlorine gas Chlorine
water
KCl (aq)
AgCl (s)
Bromine
Liquid
Bromine
water
KBr (aq)
AgBr (s)
Iodine
Vapour
Iodine water KI (aq)
AgI (s)
Know them CLEARLY
Chlorine gas Chlorine
Pale Green water
Colourless
KCl (aq)
Colourless
AgCl (s)
White
Bromine
Liquid
Red/orange
Bromine
water
KBr (aq)
Colourless
AgBr (s)
Cream
Iodine
Vapour
Violet
Iodine water
KI (aq)
Colourless
AgI (s)
Yellow
Vacuum Filtration

Draw a labelled diagram to show the
apparatus needed to perform a vacuum
filtration
Identifying Reactions
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A) H2SO4 (aq) + Ca(OH)2 (aq)  CaSO4 (aq) +
H2O (l)
B) BaCl2 (aq) + CuSO4 (aq)  BaSO4 (s) +
CuCl2 (aq)
C) Fe2O3 (s) + 3CO (g)  2Fe + 3CO2 (g)
Which equation is acid base and which is
redox?
What type of reaction is the other?
Answers
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Eqn 1 was acid base
Eqn 2 was precipitation
Eqn 3 was redox
More on acids

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What is the definition of an acid in terms of
protons.
Identify the acid and base in the following
reaction:
3Na2O + 2H3PO4  2Na3PO4 + 3H2O
Acids

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Na2O is the base (proton acceptor)
H3PO4 is the acid (proton donor)
Describe the main steps in finding the
unknown concentration of an acid by titration
(5 marks)(+1 QWC mark)
Performing a titration
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Make up a standard solution of alkali, whose
concentration you know exactly
Pipette eg 25cm3 of this into a conical flask
Place the acid in a burette, and run through
to ensure no air bubbles
Add three drops of appropriate indicator
Repeat until concordance achieved
Performing a titration

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Use a white tile
Any other suggestion- swirling flask, inverting
standard solution, rinsing glassware
QWC mark for using 3 scientific terms
appropriately and spelt correctly
Giant Covalent stuff

Explain why CO2 and SiO2 have such
different properties despite both being in
group 4 (4 marks)
Giant covalent stuff
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CO2 is simple covalent molecules, with weak
intermolecular forces between the molecules
(and strong covalent bonds within the
molecule)
SiO2 is a giant covalent network with strong
covalent bonds between the atoms.
CO2: low bp, SiO2: high bp because much less
energy needed to overcome weak imf in CO2
to separate molecules
Please note
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There are plenty of storylines that you also
need to know for this topic- including:
Redox chemistry to extract Br from sea water
Safety associated with handling/ transporting
hazardous substances like Br
The major stages of mineral extraction
The environmental impact of mineral mining