Groups 1,2, and 7 IAL Edexcel Chemistry

What is the trend in boiling point of HCl, HBr and HI?

Boiling temperature increases as number of electrons increases per molecule

Results in an increase in London forces
Pd-Pd interactions decrease

Trend in reactivity of group 1 and group 2

Reaction increases down the group

Atom size increases down group (atomic radius increases)
Ionisation energy decreases down group
(More e shielding)
Easier to lose outer electron down group

What is the trend in reaction of group 2 elements with oxygen

More vigorous down the group
Heat is required for reaction to start otherwise slow reaction

Without heat group 2 metals forms surface coating of oxide ( to prevent further oxidation)

Barium is the most reactive

What is the equation of group 2 elements with water?

Equation: M(s) + 2H₂O(l) → M(OH)₂ (aq) + H₂ (g)

Reaction of group 1 and 2 oxides with water

Group 1 and 2 oxides are basic oxides that react with water to form alkali

Solubility of hydroxides and sulfates down group 2?

Hydroxides - increases

Sulfates- decreases

Why does pH increase for hydroxides of group 2 down the group

Solubility of group 2 hydroxides increases down group
Concentration of OH- ions increases down group

Why do group 2 nitrates and carbonates react differently from group 1 chlorides

Charge of group 2 cations is double of group 1 cations
Size of group 2 cations are smaller than group 1 cations
Nitrate (NO3-) and carbonates (CO3^2-) anions are more complex than Cl-

Going down group 1 and Group 2 what is the change in stability of nitrates and carbonates

More stable down the group

Equation for Lithium and Group 2 from nitrate to nitrite and observation.

LiNO₃ → LiNO₂ +NO₂ + O₂

Brown fumes
Glowing splinter reignites

Equation for Group 1 (Except Lithium) from nitrate to nitrite and observation.

Examples :Na, K

NaNO₃ → NaNO₂ + O₂

Glowing splinter reignites

Why does thermal stability increase down group 2 nitrates and carbonates

Descending group 2, charge remains same but ionic radius increases

polarising power of cation decreases

Complex anion will become less polarised, bonds in anion are under less strain (less distorted)

Requires more energy to break bond in anion so thermal stability increases down the group

methyl orange

• red in acid

• yellow in alkali

phenolphthalein

• colourless in acid

• pink in alkali

What causes colours in flame test?

When Electrons are heated they become excited and are promoted to a higher energy

Electron returns back to ground state, releasing radiation within the visible light spectrum

What is the flame colour of lithium?

red

What is the flame colour of sodium?

Yellow

What is the flame colour of potassium?

Lilac

What is the flame colour of rubidium?

Red

What is the flame colour of Caesium

Blue

What is the flame colour of beryllium?

No colour

What is the flame colour of magnesium?

No colour

What is the flame colour of calcium?

Brick red

What is the flame colour of Strontium?

Red

What is the flame colour of Barium

Apple green green

how to test for SO4 2-

Add dilute nitric acid (to remove carbonate which would form white ppt)
then add acidified aq barium nitrate
White precipitate

How to test for CO3 2-

Add dilute HCL
Bubbles of CO2 that turn limewater milky

How to test for Cl-

Add dilute nitric acid then add aq silver nitrate
White ppt forms
Soluble in dilute ammonia

How to test for Br-

Add dilute nitric acid then add aq silver nitrate
Cream ppt forms
Soluble in concentrated ammonia

how to test for iodide ions

Add dilute nitric acid then add aq silver nitrate
Yellow ppt forms
Insoluble in dilute/concentrated ammonia

How to test for ammonium ions?

Add aq sodium hydroxide
Warm gently
Bubbles of ammonia gas are given
Turn damp red litmus paper blue

how to test for ammonia gas

Turns damp red litmus paper blue

How to test for carbon dioxide

Bubble the gas through limewater (calcium hydroxide)
Limewater turns milky

How to test for chlorine gas

Bleaches damp litmus paper

Test for hydrogen gas

Insert a lighted splint
It pops

Test got oxygen gas

Insert a glowing splint
It relights

Test for nitrogen dioxide gas

Toxic brown gas
Acidic splution formed when dissolved in water

Why does magnesium produce no colour in the flame test?

because the energy emitted is outside the visible spectrum

how are the flame colours caused

• the heat causes the electron to move to a higher energy level

• the electron is unstable at this energy level so falls back down

• energy is emitted in the form of visible light energy

How is a flame test carried out?

Dip the loop nichrome/platinum wire in HCL acid
Then dip it in solid sample

Appearance of fluorine at room temperature

Yellow gaa

Appearance of chlorine at room temperature

Green gas

Appearance of bromine at room temperature

Red brown liquid

appearance of iodine at room temperature

Grey soilid
Purple in hydrocarbon solvents
Red brown solution in water

Chlorine and concentrated sulfuric acid

H₂SO₄ (l) + NaCl (s) → HCl (g) + NaHSO₄ (s)      

• The HCl gas produces is seen as white fumes 

Bromide ions with concentrated sulfuric acid

• H₂SO₄ (l) + NaBr (s) → HBr (g) + NaHSO₄ (s)

• 2HBr (g) + H₂SO₄ (l) → Br₂ (g) + SO₂ (g) + 2H₂O (l)

• The bromine is seen as a reddish-brown gas

Iodide ions with concentrated sulfuric acid

• H₂SO₄ (l) + NaI (s) → HI (g) + NaHSO₄ (s)

• 2HI (g) + H₂SO₄ (l) → I₂ (g) + SO₂ (g) + 2H₂O (l)

• Iodine is seen as a violet/purple vapour

• 6HI (g) + H₂SO₄ (l) → 3I₂ (g) + S (s) + 4H₂O (l)

• Sulfur is seen as a yellow solid

• 8HI (g) + H₂SO₄ (l) → 4I₂ (g) + H₂S (s) + 4H₂O (l)

• Hydrogen sulfide has a strong smell of bad eggs

Reactions with hydrogen halides

• react with ammonia gas to form ammonium halides 

• react with water to produce acids

hydrogen halide + ammonia gas

NH₃ (g) + HCl (g) → NH₄Cl (s) 

hydrogen halide + water

hydrogen chloride also dissolves in water to form hydrochloric acid 

• HCl (g) → H⁺ (aq) + Cl^- (aq)