2.2 G2 + G7 Elements

Group 2 elements

Group 2 elements

What is the trend in Mp down G2 (+exception)

Down the group Mp decreases

• Aside from Mg which has the lowest G2 Mp

Give 3 G2 metals typically used in real life applications:

• Include their compounds

• Use of the compound

1. Magnesium:

• Mg → Titanium Extraction

• Mg(OH)₂ → Acid reflux prevention

2. Calcium:

• CaO/CaCO₃ → Acid rain prevention

• Ca(OH)₂ → Neutralise acidic soil

3. Barium:

• BaSO₄ → X-Ray imaging

• BaCl₂ → Test for Sulfate ions

Give the 2 equations for the extraction of Titanium

• Include state symbols

1. TiO₂(s) + 2Cl₂(g) + 2C(s) → TiCl₄(l) + 2CO (or 2CO₂ - at T<800 Celsius)

2. TiCl₄(l) + 2Mg → Ti(s) + 2MgCl₂

Give the equations for:

• Sulfur Trioxide formation

• Sulfur Trioxide → Sulfuric Acid

• 2 SO₂ + O₂ → 2 SO₃ (all gaseous)

• SO₃(g) + H₂O(l) → H₂SO₄(aq)

What is the displayed formula for Acid rain?

H₂SO₄(aq) —→ Condenses into clouds then releases as acid rain

What method do we use to prevent Acid Rain?

• Products formed?

Wet Scrubbing:
Mix CaO or CaCO₃ + water to form a slurry and spray this onto the acidic Sulfur Dioxide gas:

• Both form solid CaSO₃

• Calcium carbonate forms CO₂ with CaSO₃

What is the trend in solubility down the G2 Hydroxides?

Solubility down the group increases i.e:

Beryllium Hydroxide is insoluble

How is Mg(OH)₂ used to prevent Acid Reflux? (why)

Magnesium Hydroxide can be made into a small pill form, dissolve and neutralise acidity + not corrode the organs:

• Magnesium Hydroxide has low solubility, so can do this safely

How is Ca(OH)₂ used to neutralise soil?

• (+equation → use HCl as an example)

Maintains pH by reacting with acid, since Calcium Hydroxide is basic:

• Ca(OH)₂ (s) + HCl (aq) → CaCl₂ (aq) + 2H₂O (l)

How is Ba(SO)₄ used in X-ray imaging? (explain + why is it safe)

Barium Sulfate is dense and coats the organs, allowing a solid image to be formed in the X-ray:

• Barium sulfate is highly insoluble so isn’t absorbed by the body to damage it - despite barium forming toxic compounds

How is BaCl₂ used to test for sulfates?

• Precipitate formed (equation)

• Other reagents (why use these)

• Which 2 reagents dont we use (why)

White BaSO₄ precipitate formed when positive:

• BaCl₂ + XSO₄(aq) → 2XCl(aq) + BaSO₄
  (where X is any element)

• Add dilute HCl when carrying out experiment to react with unwanted carbonates, to prevent Barium carbonate precipitate formation - which is also white and can give false results

dont use: NO₃^- or OH^- , as they remove the Carbonates but form an unwanted Barium precip

G7 Halides

G7 Halides

What are the colours and states of the G7 elements?

• F₂ = Pale yellow gas

• Cl₂= Green gas

• Br₂= Red-Brown Liquid

• I₂= Dark grey solid

What is the trend in electronegativity down G7? (why)

Decrease:

Size of atoms increase so there is a greater distance between electrons in a bond + nucleus

What is the trend in Bp down the group? (why)

Increase:

Size of atoms increase so there is a greater VDW forces

What is the trend in Reduction/Oxidation agents down the group?

• Reduction (agent) increases down the group

• Oxidation (agent) decreases down the group

What is the test for halides?

• Reagents + why use these

• Positive result colours for halides (+with dilute/conc ammonia solution)

Silver nitrate reacts with halides to form coloured precipitate, add nitric acid when testing to react with unwanted carbonate ions:

• Fluorine = No precipitate

• Chlorine = White → Dissolve with dilute + fast with conc ammonia solution

• Bromine = Cream → Dissolve with conc ammonia solution

• Iodine = Yellow → No dissolving with conc ammonia solution

What is a Practical use of Sulfates?

Good drying agents

Sodium Halides + Sulfuric acids

Sodium Halides + Sulfuric acids

What are the reactions of Sulfuric acid with:

• NaF

• NaCl

• Both form NaHSO₄

• HF or HCl → depending on the corresponding salt

What are the 2 reactions with Sulfuric acid with:

• NaBr

• Observations

• WHY DOES THIS OCCUR

• 1. NaBr + H₂SO₄ → NaHSO₄ + HBr
  2. 2HBr + H₂SO₄ → SO₂ + 2H₂O + Br₂

• Brown steamy fumes

• Bromine is more reducing than F and Cl so it reacts again with sulfuric acid acting as a reducing agent
  

What are the 2 reactions with Sulfuric acid with:

• NaI

• Observations (3)

• WHY DOES THIS OCCUR

• 1. NaI + H₂SO₄ → NaHSO₄ + HI
  2. 8HI + H₂SO₄ → 4I₂ + H₂S + 4H₂O

• Rotten egg smell, dark grey precipitate , temporary yellow precip due to Sulfur appearing

• As Sulfur reduces from Sulfuric acid to Sulfur Dioxide to Sulfur to Hydrogen Sulfide, the Sulfur gives the yellow precipitate, the grey from iodine and smell from H₂S

Extra Cl reactions

Extra Cl reactions

What is the reaction between Cl w/ Cold, Dilute NaOH?

Cl₂ + 2NaOH → NaCl + NaClO + H₂O

What is the reaction between Cl w/ Hot, Concentrated NaOH?

3Cl₂ + 6NaOH → 5NaCl + NaClO₃ + 3H₂O