MODULE 3
15
WORKSHEET
WORKSHEET
PRECIPITATION REACTIONS
AND SOLUBILITY
Syllabus reference 8.4.4
1
Match the terms on the left with the correct definition.
TERM
2
DEFINITION
Dissociation
Solubility
A measure of the maximum amount of substance that will
dissolve in a given amount of solvent at a particular temperature.
Saturated
Dissolution
The breaking up of the particles in a solid by dissolving in a
solvent.
Insoluble
Saturated
A solution in which no more solute will dissolve at a particular
temperature.
Unsaturated
Dissociation
The separation of an ionic solid into its anions and cations in
solution or molten state.
Solubility
Precipitation
The formation of a solid when two solutions are mixed.
Dissolution
Insoluble
Not able to be dissolved in a given solvent.
Precipitation
Unsaturated
A solution which contains less than the maximum amount of
solute.
A student was investigating the solubility of potassium nitrate (KNO3) at different temperatures.
The amount of solvent (water) was kept constant at 100 g. The amount of solute needed to
produce a saturated solution was recorded in the table below.
Temperature of water (°C)
10
20
30
40
50
60
70
80
Mass of solute (g)
18
29
44
62
80
105
130
160
Copyright © 2008 McGraw-Hill Australia
CONQUERINGCHEMISTRY PRELIM
MODULE 3 WS 15
a
Draw a graph of solubility versus temperature on the grid below.
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b
Would points on the graph below the curve represent a saturated or unsaturated solution?
Unsaturated
c
Write a balanced equation to show the dissociation of KNO3 in water.
KNO3(s) → K(aq)  NO3(aq)
d
How much KNO3 will dissolve in 200 g of water at 65°C?
From the graph 116 / 1g dissolve in 100 g water at 25ºC so 232 / 2g will dissolve in
200 g water at 25ºC.
Copyright © 2008 McGraw-Hill Australia
CONQUERINGCHEMISTRY PRELIM
MODULE 3 WS 15
e
If 25 g of KNO3 was dissolved in 100 g of water at 25°C, how much more KNO3 must be
added to make a saturated solution at that temperature?
From the graph 36 / 1 g will dissolve in 100 g water at 25ºC so another 11 / 1 g will
dissolve.
f
What is the minimum mass of water at 45°C needed to dissolve 20 g of KNO3?
From the graph 72 / 1 g will dissolve in 100 g water at 45ºC.
Mass of water needed to dissolve 20 g  20/72  100  28 mL.
3
Use the solubility table from your textbook to determine whether or not a precipitation
reaction will occur when the following reactants are mixed. Where a reaction occurs write the
balanced neutral species equation for the reaction.
a potassium chloride and zinc nitrate
no precipitate
b
ammonium bromide and lead nitrate
precipitate
2NH4Br(aq)  Pb(NO3)2(aq) → PbBr2(s)  2NH4NO3(aq)
c
ammonium sulphide and magnesium acetate
no precipitate
d
strontium chloride and zinc sulfate
precipitate
SrCl2(aq)  ZnSO4(aq) → SrSO4(s)  ZnCl2(aq)
4
Write balanced ionic equations for the reactions that occur when the following solutions are
mixed:
a barium chloride and sodium sulfate
Ba2(aq)  SO42(aq) → BaSO4(s)
b
copper(II) sulfate and potassium hydroxide
Cu2(aq)  2OH(aq) → Cu(OH)2(s)
c
calcium chloride and sodium carbonate
no precipitate
d
silver nitrate and sodium chloride
Ag(aq)  Cl(aq) → AgCl(s)
e
lead(II) nitrate and potassium iodide
Pb2(aq)  2I(aq) → PbI2(s)
Copyright © 2008 McGraw-Hill Australia
CONQUERINGCHEMISTRY PRELIM
MODULE 3 WS 15
5
What solutions would you mix to produce each of the following precipitates?
a lead sulfate
lead(II) nitrate and sodium sulfate
b
iron(II) silfide
iron(II) nitrate and potassium sulfide
c
magnesium hydroxide
magnesium nitrate and sodium hydroxide
Copyright © 2008 McGraw-Hill Australia
CONQUERINGCHEMISTRY PRELIM
MODULE 3 WS 15