Solubility of Salts

State the solubility and the colour of Iron (III) hydroxide， Fe(OH)3

• Soluble Salt, Brown Colour

• Insoluble Salt, Brown Colour

• Soluble Salt, Green Colour

• Insoluble Salt, Green Colour

Answer explanation

Iron (III) hydroxide, Fe(OH)3, is an insoluble salt (Because all hydroxide are insoluble, unless pair with SPA, but there is no SPA in it)

Iron (III) ions are brown in colour

State the solubility of Silver Chloride , AgCl

• Soluble Salt

• Insoluble Salt

Answer explanation

Silver Chloride (AgCl) is an Insoluble Salt.
All chloride salt are soluble, except PAH

State the solubility of Magnesium sulphate, MgSO4

• Soluble Salt

• Insoluble Salt

State the solubility of Lead Nitrate, Pb(NO3)2

• Soluble Salt

• Insoluble Salt

State the solubility and the colour of Copper (II) Hydroxide

• Soluble, Blue Colour

• Insoluble, Blue Colour

• Soluble Salt, Brown Colour

• Insoluble Salt, Brown Colour

Answer explanation

All hydroxide salt are insoluble, except pair with SPA, but there is no SPA in it.

Copper (II) ions are Blue colour

All Sulphate salts are soluble, except

• S, P, A

• Pb, Ba, Ca

• Pb, Ag, Hg

• Pb,Ba,Co

Which of the following are soluble salts?

• Potassium oxide, K2O

• Lead (II) Chloride, PbCl2

• Zinc Carbonate, ZnCO3

• Barium Chloride, BaCl2

Answer explanation

Soluble salts are compounds that dissolve in water. Potassium oxide (K2O) and Barium Chloride (BaCl2) are soluble salts, while Lead (II) Chloride (PbCl2) and Zinc Carbonate (ZnCO3) are insoluble.

Rules 1: All SPA are soluble -- (P) -- Potassium -- soluble
Rules 2: All chloride are soluble except PAH -- (Pb) Lead -- insoluble, (Ba) Barium is not in the list, thus Barium chloride is soluble

**Barium is only insoluble when pair with sulphate

Pick the suitable acid and alkali to form the salt - Ammonium Chloride

• Hydrochloric acid

• Potassium hydroxide

• Ammonia

• Nitric Acid

Answer explanation

To form Ammonium Chloride, we need to react Ammonia (an alkali) with Hydrochloric acid (an acid). Therefore, the suitable acid and alkali to form Ammonium Chloride are Hydrochloric acid and Ammonia.

Ammonia --- contribute ammonium ions (NH4 +)
Hydrochloric acid -- contribute chloride ions (Cl -)

Pick the suitable acid and alkali to form the salt - Copper (II) Sulphate

• Hydrochloric acid

• Sulphuric acid

• Copper (II) Oxide

• Sodium hydroxide

Answer explanation

To form Copper (II) Sulphate, we need to react Copper (II) Oxide with Sulphuric acid. Copper (II) Oxide contribute Copper (II) ions, while sulphuric acid contribute sulphate ions

Construct a balanced chemical equation to produce Zinc Nitrate, Zn(NO3)2

Tips:
1. Select carefully the acid and alkali needed to produce the salt above.
Acid - contribute the anions (negative ions)
Alkali - contribute the cations (positive ions)

Answer explanation

Alkali - Zinc Oxide --- Contribute Zinc ions (Zn 2+)

Acid - Nitric Acid --- Contribute Nitrate ions (NO3 -)