7/30/2019 Chemical Equations Worksheet Answers 2

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Oxley College - Science

Precipitation reactions

Every substance is soluble in water to some extent but obviously some substances are more soluble thanothers. If two ionic substances are mixed together they will generate four different kinds of ions in solution.

e.g. Lead II nitrate, Pb(NO 3)2, is mixed with potassium iodide, KI

It happens that potassium iodide, lead II nitrate and potassium nitrate are all very soluble but that lead iodideisnt. What happens is that, since all the ions and the water molecules are in constant motion, the lead ionsbump into iodide ions, join with them and fall out of the solution. They form a precipitate (which happens tobe canary yellow). All the other ions are left in the solution.

The reaction in words:potassium iodide (in solution) + lead II nitrate (in solution) lead iodide (solid) + potassium nitrate (in

solution)

In symbols: KI (aq) + Pb(NO 3)2 (aq) PbI 2 (s) + KNO 3 (aq)

and balanced: 2 KI (aq) + Pb(NO 3)2 (aq) PbI 2 (s) + 2 KNO 3 (aq)

Note that the abbreviation (aq) means aqueous i.e. dissolved in water while (s) means solid.

Some solubility rules:Soluble Not very soluble

all salts of ammonia , sodium , lithiumand potassium

all nitrates

all acetates

most sulfates (except calcium, barium,

mercury, lead and silver)sodium, lithium, ammonium andpotassium hydroxides

most chlorides (except lead andsilver)

all sulfides (except sodium, lithiumand potassium

calcium, barium, mercury, lead andsilver sulfates

all oxides (except sodium. lithium and

barium)most salts of lead and silver (exceptfor nitrates and acetates)

all silicates (except sodium, lithiumand potassium

Another example : sodium sulfide is mixed with calcium chloride

The extra possible combinations of ions are: sodium with chloride and calcium with sulfide

A look at the table reveals thatcalcium sulfide

isnt very soluble and will become a precipitate

The reaction in symbols is: Na 2S (aq) + CaCl 2 (aq) CaS (s) + 2 NaCl (aq)

Year 10 Science Worksheet on writin chemical

Pb 2+NO 3-

I -

NO 3-

K +

K +

I -

7/30/2019 Chemical Equations Worksheet Answers 2

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Now try writing equations for these :

(Of course youll have to work out the correct formula of each salt and also studythe table of solubilities)

1. Calcium chloride solution is mixed with magnesium sulfate solutionIn symbols

CaCl 2(aq) + MgSO 4(aq) CaSO 4(s) + MgCl 2(aq)

2. Sodium chloride solution is mixed with lead II acetate solutionIn symbols

2NaCl (aq) + Pb(CH 3COO) 2(aq) PbCl 2(s) + 2CH 3COONa (aq)

3. Silver nitrate solution is mixed with potassium chloride solutionIn symbols

AgNO 3(aq) + KCl (aq) AgCl (s) + KNO 3(aq)

4. Aluminium sulfate solution is mixed with sodium hydroxide solutionIn symbols

Al2(SO 4)3(aq) + 6NaOH (aq) 2Al(OH) 3(s) + 3Na 2SO 4(aq)

5. Lithium hydroxide solution is mixed with iron II chloride solutionIn symbols

2LiOH (aq) + FeCl 2(aq) Fe(OH) 2(s) + 2LiCl (aq)

6. Aluminium chloride solution is mixed with lead II acetate solutionIn symbols

2AlCl 3(aq) + 3Pb(CH 3COO) 2(aq) 3PbCl 2 (s) + 2Al(CH 3COO) 3(aq)

7. Iron III sulfate solution is mixed with barium hydroxide solutionIn symbols

Fe 2(SO 4)3(aq) + 3Ba(OH) 2(aq) 2Fe(OH) 3(s) + 3BaSO 4(s)

8. Sodium silicate solution is mixed with calcium chloride solutionIn symbols

Na 2SiO 3(aq) + CaCl 2(aq) CaSiO 3(s) + 2NaCl (aq)

9. Magnesium chloride solution is mixed with silver nitrate solutionIn symbols

MgCl 2(aq) + 2AgNO 3(aq) 2AgCl (s) + Mg(NO 3)2(aq)

10. Ammonium sulfate solution is mixed with barium chloride solutionIn symbols

(NH 4)2SO 4(aq) + BaCl 2(aq) BaSO 4(s) + 2NH 4Cl (aq)