chemistry 4.5 - reactions of halides

How does the reductions ability of group 7 change down the group?

Increases as it is easier to lose electrons

What is formed when potassium fluoride and chloride reacts with sulphuric acid?

Potassium hydrogen sulphate (s) and hydrogen fluoride or chloride (g)

What is formed when potassium bromide reacts with sulphuric acid?

Potassium hydrogen sulphate and hydrogen bromide

The hydrogen bromide then reacts further with the sulphuric acid to form bromine gas + sulphur dioxide (g) + water (l)

What is formed when potassium iodide reacts with sulphuric acid?

Potassium hydrogen sulphate and hydrogen iodide

The hydrogen iodide then reacts further with the sulphuric acid to form iodine (s) + sulphur dioxide (g) + water (l)

Hydrogen iodide will also react with the sulphur dioxide to form hydrogen sulphide (g) + iodine (s) + water (l)

Why were there extra steps added down the group in these reactions?

The halides became stronger reducing agents so can reduce more things

What are hydrogen halides?

Acidic gases

What happens when hydrogen halides are added to water and what is this reaction for hydrogen chloride?

They dissolve or produce misty fumes of acidic gases

HCl (g) + H2O (l) → H3O+ (aq) + Cl- (aq)

Hat are the names for aqueous hydrogen halides

Hydrochloric acid, hydrobromic acid, hydroiodic acid

Hat happens when hydrogen halides are exposed to ammonia gas and what is the equation for HCl?

White fumes are produced

HCl (g) + NH3 → NH4Cl (s)

At do you do when testing for halides?

Add dilute nitric acid to remove ions that could interfere and then add silver nitrate to from silver halides which are solids

What colour precipitate is silver fluoride and what does it dissolve in?

No precipitate as AgF is soluble

What colour precipitate is silver chloride and what does it dissolve in?

White dissolves in dilute ammonia to form a colourless solution

What colour precipitate is silver bromide and what does it dissolve in?

Cream, dissolves in concentrated ammonia to form a colourless solution

What colour precipitate is silver iodide and what does it dissolve in?

Yellow, doesn’t disolver in any concentration of ammonia