Chemistry - GROUP 7 REACTIONS

What happens to electronegativity down the group and why ?

Decreases. Shared electrons get further away from nucleus as atoms get larger and increases shielding as more inner shells of electrons

What happens to melting and boiling points down the group and why ?

Increase. Atoms larger so have more electrons so have stronger VDW forces between molecules.

How does oxidising ability change down the group ?

Decreases.Atoms larger so shared electrons further from nucleus so more shielding so harder to accept an electron.

What halide ions will F2 displace?

Cl -

Br -

I -

What halide ions will Cl2 displace ?

Br -

I -

What halide ions will Br2 displace?

I -

What halide ions will I2 displace ?

none

How does reducing ability of halide IONS change down the group?

Increases. Atoms get bigger so more easily lose an electron.

Which sodium halides react with concentrated sulfuric acid ?

NaCl

NaBr

NaI

Give an equation for the reaction of solid sodium chloride with concentrated sulfuric acid , what type of reaction is this and why

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

Acid - Base

Not redox because no oxidation state has changed

Give the 2 reactions from the reaction of solid sodium bromide with concentrated sulfuric acid , what type of reaction they are and why

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

Acid -Base reaction

2H+ +2Br- +H2SO4 (l) → SO2 (g) + 2H2O (l) +Br2 (l)

Redox - bromide ions strong enough reducing agents to reduce sulfuric acid to sulfur dioxide

Give 2 of the reactions of solid sodium iodide and concentrated sulfuric acid , what type of reaction they are and why

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

Acid - base

8H+ +8I- + H2SO4 → H2S (g) + 4H2O (l) + 4I2 (s)

Iodide ions are better reducing agents than bromide ions so reduce sulfur in sulfuric acid even further to form SO2 , S or HS gas

Colour and further test for silver chloride

white ppt

dissolves in dilute ammonia

Colour and further test for silver bromide

cream ppt

dissolves in conc ammonia

Colour and further test for silver iodide

pale yellow ppt

insoluble in conc ammonia

What can be used to test for halide ions ?

Silver ions eg in silver nitrate

Write an equation for the reversible reaction of Cl2 with water

what type of reaction is this

Cl2 (g) + H2O (l) → (reversible) HClO (aq) +HCl (aq)

Disproportionation

What reaction occurs between chlorine and water in sunlight (UV) ? write an equation

2Cl2 (g) + 2H2O (l) → 4HCl (aq) + O2 (g)

Write an equation for the reversible reaction of solid NaClO with water

NaClO (s) + H2O → (reversible) Na+ (aq) + OH- (aq) + HClO (aq)

Write an equation for the reaction of chlorine with cold dilute sodium hydroxide to form sodium chloride

Cl2 (g) + 2NaOH (aq) → NaClO (aq) + NaCl (aq) + H2O (l)

What is chloric acid used for ?

Kills bacteria (oxidising agent)