ES 6 Hydrogen chloride in industry and the laboratory

What is a simple method of making hydrochloric acid?

mixing H and Cl directly

What is atom economy?

the proportion of reactants that become desired products

How can you calculate percentage atom economy?

(Mr desired product/ Mr reactants) x 100

How is HCl gas produced during PVC production?

1. ethene reacts with chlorine to make 1,2-dichloroethane

2. thermal cracking of 1,2-dichlororethane forms chloroethene and hydrogen chloride

Reaction of thermal cracking of 1,2-dichloroethene

CH_₂ClCH_₂Cl → CH_₂CHCl + HCl

How is hydrochloric acid formed from hydrogen chloride?

dissolving in water

What kind of ions does hydrogen chloride form when dissolved in water?

hydrated H⁺ and Cl^-

Order the Group 7 elements in terms of least to strongest oxidising agent

I_₂

Br_₂

Cl₂

F_₂

Order the Group 7 ions in terms of least to strongest reducing agents

F^-

Cl^-

Br^-

I^-

Reaction of sodium chloride/sodium fluoride with sulfuric acid

NaCl (s) + H₂SO₄ (aq) —→ NaHSO_₄ (aq) + HCl (g)

What can you see in the reaction of sodium chloride with hydrogen chloride gas?

white fumes of hydrogen chloride as it meets moist air and forms hydrochloric acid

reaction of sodium bromide with sulfuric acid?

NaBr (s) + H_₂SO_₄ (aq) → NaHSO_₄ (aq) + HBr (g)

What does HBr reduce sulfuric acid to?

sulfur dioxide

How can you detect sulfur dioxide?

smells like burning matches

Reaction of HBr reducing sulfuric acid

2H^⁺ (aq) + 2Br⁻ (aq) + H_₂SO_₄ (aq) → SO_₂ (g) + Br_₂ (l) + 2H_₂O (l)

Why is sulfuric acid reduced to sulfur dioxide?

Bromide ions are strong reducing agents

Is the reaction of sodium bromide and sulfuric acid exothermic or endothermic?

exothermic

What is the gas produced in reaction of sodium bromide and sulfuric acid made of?

hydrogen bromide

sulfur dioxide

bromine vapour

reaction of sodium iodide with sulfuric acid

NaI (s) + H_₂SO_₄ (aq) —→ NaHSO_₄ (aq) + HI (g)

What does HI reduce sulfuric acid to?

hydrogen sulfide gas

Reaction of HI reducing sulfuric acid

8H^⁺ (aq) + 8I⁻ (aq) + H_₂SO_₄ (aq) —→ H_₂S (g) + 4I_₂ (s) + 4H_₂O (l)

Stronger reducing agents ______________ the oxidation number ________.

reduce

more

What does hydrogen sulfide smell of?

rotten eggs

What kind of acid s used to make hydrogen chloride with sodium chloride and why?

sulfuric acid

chloride ions are not strong reducing agents so the product is pure

What kind of acid is used to make hydrogen bromide/iodide with sodium bromide/iodide and why?

phosphoric acid

it wont be reduced so product is pure

What is the trend in thermal stability of hydrogen halides down the group?

decreases

Why does the thermal stability of hydrogen halides decrease down the group?

bond strength between hydrogen and halogen decreases

less energy is needed to break bonds

What happens to hydrogen fluoride when it is heated?

is not broken down

What happens to hydrogen chloride when it is heated?

is not broken down

What happens to hydrogen bromide when it is heated?

some bromine gas is made

What happens to hydrogen iodide when a red hot needle is plunged in?

large amounts of purple gaseous iodine are made

Are hydrogen halides acidic?

yes

Which hydrogen halide is the least acidic?

HF

What is the percentage dissociation of most hydrogen halides in water?

100%

Equation for dissociation of HCl in water using H⁺ ions

HCl (aq) —→ H^⁺ (aq) + Cl⁻ (aq)

Equation for dissociation of HCl in water using oxonium ions

H_₂O (l) + HCl (aq) —→ H_₃O^⁺ (aq) + Cl⁻ (aq)

What does reacting ammonia with hydrogen halides make?

ammonium halides

How do you detect ammonium halides?

white cloud

Reaction of ammonia with HCl

NH_₃ (g) + HCl (g) —→ NH_₄Cl (s)