Qualitative Analysis

What is the use of qualitative analysis?

To identify unknown cations and anions through the formation of ppt and gases.

What physical tests can identify unknown substances?

• Observe colour of substance • Test its solubility in water

What is the chemical test for carbonate (CO₃²⁻)?

• Add nitric acid • Effervescence observed. Gas forms white ppt with limewater.

What is the equation for CO₂ reacting with limewater?

Ca(OH)2​(aq)+CO2​(g)→CaCO3​(s)+H2​O(l)

What is the solubility rule for chlorides?

All chlorides are soluble except silver chloride and lead chloride.

How do you test for chloride (Cl⁻)?

• Add nitric acid • Add aqueous silver nitrate • White ppt (AgCl) formed.

What is the solubility rule for iodides?

All iodides are soluble except silver iodide and lead iodide.

How do you test for iodide (I⁻)?

• Add nitric acid • Add aqueous silver nitrate • Pale yellow ppt (AgI) formed.

What is the solubility rule for sulfates?

All sulfates are soluble except barium sulfate, calcium sulfate, lead sulfate.

How do you test for sulfate (SO₄²⁻)?

• Add nitric acid • Add aqueous barium nitrate • White ppt (BaSO₄) formed.

What is the test for nitrate (NO₃⁻)?

• Add aqueous sodium hydroxide and aluminium foil • Warm mixture • Ammonia gas turns red litmus blue.

What reagents identify cations?

Aqueous sodium hydroxide and aqueous ammonia.

How is NH₄⁺ identified?

• Add aqueous sodium hydroxide • Warm mixture • Ammonia gas turns red litmus blue.

What is observed when NaOH is added to Cu²⁺?

(a) Pale blue ppt (b) Insoluble in excess.

What happens when NH₃ is added to Cu²⁺?

(a) [Not specified] (b) [Not specified]

What is observed with Fe²⁺ and NaOH?

(a) Green ppt (b) Insoluble in excess.

What is observed with Fe³⁺ and NaOH?

(a) Red-brown ppt (b) Insoluble in excess.

What happens when NaOH is added to Al³⁺?

(a) White ppt (b) Dissolves in excess NaOH to form colourless solution.

What happens when NH₃ is added to Al³⁺?

(a) White ppt (b) Insoluble in excess.

What is observed with Zn²⁺ and NaOH?

(a) White ppt (b) Dissolves in excess NaOH to form colourless solution

What is observed with Fe²⁺ and NH3?

(a) green ppt (b) insoluble in excess

What is observed with Fe³⁺ and NH3?

a) red-brown ppt (b) insoluble in excess

What is observed when NaOH is added to Ca²⁺?

(a) white ppt (b) insoluble in excess

What is observed when NH3 is added to Ca²⁺?

No ppt/ No observable chnage

What is observed when NH3 is added to Zn²⁺?

(a) white ppt (b)