Colorful Precipitation Reactions

A precipitation reaction is a reaction in which two solutions are mixed to produce an insoluble solid called a precipitate.

Simplified Solubility Rules :If a compound contains one of the following chemicals it is always soluble

Physical states
(aq) = aqueous and (s) = solid

Student Instructions

• Complete the word equation for each precipitation reaction.
• Write a balanced equation for each reaction. Use the valencies below to help you.

• Include physical states(aq) or (s) in your chemical equation.
• Use the simplified solubility rules to determine the solid precipitate

1. Sodium hydroxide + silver nitrate sodium nitrate +  silver hydroxide (brown)

NaOH(aq) + AgNO₃(aq) NaNO₃(aq) + AgOH(s)

2. Sodium hydroxide + copper sulfate sodium sulfate + copper hydroxide (blue)

2NaOH(aq) + CuSO₄(aq) Na₂SO₄(aq) + Cu(OH)₂(aq)

3. Potassium iodide + lead nitrate potassium nitrate + lead iodide (yellow)

2KI(aq) + Pb(NO₃)₂(aq) 2KNO₃(aq) + PbI₂(s)

4. Potassium iodide + mercury nitrate mercury iodide (orange) + potassium nitrate

2KI(aq) + Hg(NO₃)₂(aq) HgI₂(s) + KNO₃(aq)

5. Potassium iodide + silver nitrate potassium nitrate + silver iodide (white/ yellow)

KI(aq) + AgNO₃(aq) KNO₃(aq) + AgI(s)

6. Sodium chloride + silver nitrate sodium nitrate + silver chloride (white)

NaCl(aq) + AgNO3(aq) NaNO₃(aq) + AgCl(s)

7. Mercury nitrate  + potassium fluoride mercury fluoride + potassium nitate

Hg(NO₃)₂(aq) + 2KF(aq) HgF₂(aq) + 2KNO₃(aq)

8. Copper sulfate + potassium iodide copper(II) iodide + potassium sulfate

CuSO₄(aq) + 2KI(aq) CuI₂(s) + K₂SO₄(aq)

Note: The above reaction is more complex. Copper(I) iodide, CuI is formed with iodine, I₂(aq)

This equation is technically correct. 2CuSO₄(aq) + 4KI(aq) 2CuI(s) + 2K₂SO₄(aq) + I₂(aq) (overall brown/ red)

The iodine ions reduce the copper(II) ions to copper(I).