Module 8 Stuff (kill me)

Question 1

Flame tests

What flace colour is Barium?

Answer 1

Pale green

Question 1

Flame Tests

What flame colour is Sodium?

Answer 1

Yellow

Question 2

Flame Tests

What flame colour is Calcium?

Answer 2

Brick-red

Question 3

Flame test

What flame colour is Copper?

Answer 3

Blue-green

Question 4

Tests

What is a complexation reaction and give me two you need to know?

Answer 4

a chemical reaction in which a central metal ion binds to one or more ligands (molecules or ions that donate electron pairs) to form a coordination complex.

Ag⁺ (aq) + 2 NH₃ (aq) → [Ag(NH₃)₂]⁺ (aq)

Zn²⁺ (aq) + 4 OH⁻ (aq) → [Zn(OH)₄]²⁻ (aq)

Question 5

Tests

How do you perform cation identification?

Answer 5

1. Add chloride ions (e.g. NaCl or HCl)
   Tests for cations that form insoluble chlorides.
   Look for white precipitates.

Examples:

Ag⁺ + Cl⁻ → AgCl (s) — white precipitate
Then add NH₃:
AgCl (s) + 2 NH₃ (aq) → [Ag(NH₃)₂]⁺ (aq) + Cl⁻
Precipitate dissolves → confirms Ag⁺

Pb²⁺ + 2 Cl⁻ → PbCl₂ (s) — white precipitate (dissolves in hot water)

2. Add sulfate ions (e.g. Na₂SO₄ or H₂SO₄)
   Tests for cations that form insoluble sulfates.

Examples:

Ba²⁺ + SO₄²⁻ → BaSO₄ (s) — white precipitate

Pb²⁺ + SO₄²⁻ → PbSO₄ (s) — white precipitate

🧪 If a white precipitate forms and Ba²⁺ or Ca²⁺ is suspected:

Take a new sample and add excess F⁻ (e.g. NaF).
 → If a white precipitate forms, filter it.
 → Then add SO₄²⁻ to the filtrate:

If a white precipitate forms → Both Ba²⁺ and Ca²⁺ are present.

If no precipitate forms → Only Ca²⁺ is present.

3. Add hydroxide ions (e.g. NaOH)
   Forms hydroxide precipitates with many cations.
   Observe color and solubility in excess OH⁻ or NH₃.

Examples:

Fe³⁺ + 3 OH⁻ → Fe(OH)₃ (s) — red-brown precipitate

Cu²⁺ + 2 OH⁻ → Cu(OH)₂ (s) — blue precipitate

Zn²⁺ + 2 OH⁻ → Zn(OH)₂ (s) — white precipitate
 ✔️ Add excess OH⁻:
 Zn(OH)₂ (s) + 2 OH⁻ → [Zn(OH)₄]²⁻ → precipitate dissolves → confirms Zn²⁺

Question 6

Test

How do you perform an anion identification?

Answer 6

1. Measure pH with a pH meter

Determines if the solution is acidic, neutral, or basic to help narrow anion possibilities.

For example:

Acidic: may indicate chloride (Cl⁻), nitrate (NO₃⁻), sulfate (SO₄²⁻)

Basic: may indicate carbonate (CO₃²⁻), hydroxide (OH⁻)

2. Add dilute nitric acid (HNO₃)

Tests for carbonate and sulfite by observing gas evolution (CO₂ or SO₂).

Reactions:

Carbonate:
CO₃²⁻ + 2 H⁺ → CO₂ (g) + H₂O
 ✅ Effervescence (bubbling) confirms carbonate

Sulfite:
SO₃²⁻ + 2 H⁺ → SO₂ (g) + H₂O
 ✅ Smell of sulfur dioxide and possible discoloration confirms sulfite

3. Add barium ions (e.g. Ba(NO₃)₂)

Tests for sulfate, carbonate, and phosphate by forming precipitates.

Reactions:

Sulfate:
SO₄²⁻ + Ba²⁺ → BaSO₄ (s) — white precipitate (insoluble in HNO₃)

Carbonate:
CO₃²⁻ + Ba²⁺ → BaCO₃ (s) — white precipitate (dissolves with effervescence in HNO₃)

Phosphate:
PO₄³⁻ + 3 Ba²⁺ → Ba₃(PO₄)₂ (s) — white precipitate

4. Add silver nitrate (AgNO₃)

Tests for halide ions by forming characteristic precipitates.

Reactions:

Chloride:
Cl⁻ + Ag⁺ → AgCl (s) — white precipitate
 ✔️ Add NH₃: dissolves → confirms chloride

Bromide:
Br⁻ + Ag⁺ → AgBr (s) — cream precipitate (partially soluble in concentrated NH₃)

Iodide:
I⁻ + Ag⁺ → AgI (s) — yellow precipitate (insoluble in NH₃)

Question 7

Air pollution

What are 5 pollutants and their source?

Answer 7

1. Carbon monoxide (CO): Motor cars, ciggarettes, forest and farm fires, slow combustion stoves
2. Partuculates (inclusing asbestos): Combustion, industrial processes, burn-offs, old buildings and demolation
3. Airborn lead: Lead smelters, old paint dust, Leaded petrol
   4.Radioactivity: Combustion(coal), uranium mining, nuclear weapons, nuclear power plants
4. Chlorofluorocarbons: old refrigeration, air conditioning, foam, plastics, electronic cleaning