Chemical reactions - precipitation reactions

2006 QUESTION ONE: TYPES OF REACTION
Classify each of the reactions in the table below by writing the letter from the key list in the space provided.

Key list: oxidation-reduction – O
precipitation – P
thermal decomposition – T

Type of reaction
(Choose from O, P or T)

(a)
CaCl2(aq) + K2CO3(aq) → 2KCl(aq) + CaCO3(s)
Precipitation
(b)
Pb(OH)2(s) → PbO(s) + H2O(l)
Thermal decomposition
(c)
AgNO3(aq) + NaCl(aq) → NaNO3(aq) + AgCl(s)
Precipitation
(d)
Cl2(aq) + 2I–(aq) → 2Cl–(aq) + I2(aq)
Redox
(e)
CO(g) + PbO(s) → Pb(s) + CO2(g)
Redox


2006 QUESTION TWO: PRECIPITATION
The following solutions are mixed in the pairs shown. Use the solubility rules in your Resource Booklet to identify the precipitate (if any) that is formed for each pair.

(a) Write the name of the precipitate or, if none is formed, write no precipitate.

(i)
Sodium chloride and copper nitrate --> sodium nitrate and copper chloride
no precipitate
(ii)
Lead nitrate and potassium chloride --> lead chloride + potassium nitrate
HINTS:
here the spectator ions are potassium ions and nitrate ions, these ions stay in solution and the lead and chloride ions bond to form a solid of lead chloride.

lead chloride precipitate
(iii)
Potassium hydroxide and magnesium sulfate ---> magnesium hydroxide + potassium sulfate
magnesium hydroxide precipitate


(b) Write a balanced equation for the formation of ONE precipitate identified in Question Two (a) above. Spectator ions may be omitted from ionic equations.


Pb2+ + 2Cl- ---> PbCl2

Mg2+ + 2OH- --> Mg(OH)2

When a precipitate

2007 QUESTION ONE: PRECIPITATION
The following pairs of solutions are mixed. Use the solubility rules in your Resource Booklet to identify if a precipitate is formed.

(a) Write the name of the precipitate. If none is formed, write no precipitate.

Solutions that are mixed
Name of the Precipitate, OR No Precipitate

(i)
Silver nitrate + calcium chloride --> silver chloride + calcium nitrate
silver chloride precipitate

(ii)
Potassium sulfate + iron(II) nitrate --> potassium nitrate + iron sulfate
no precipitate

(iii)
Calcium nitrate + sodium sulfate --> calcium sulfate + sodium nitrate
calcium sulfate precipitate

(b) Write a balanced equation for the formation of ONE precipitate identified in Question One (a) above. Spectator ions may be omitted from ionic equations.

Ag+ + Cl- --> AgCl