The Halogens Flashcards
Why does boiling point increase going down group 7
More electrons
Stronger London forces
More ent required to break the intermolecular forces
Boiling point increases
What is an oxidising agent
Causing another element to be oxidised increasing its oxidation number
Colour of chlorine
Pale green gas
Pale green. In water and cyclohxane
Colour of bromine
At rtp it is a red brown liquid
In water and cyclohexane it is orange
Colour of iodine
At rtp it is a shiny grey black solid
In water it is brown
In cyclohexane it is violet
Colour of fluorine
At rtp it is a pale yellow gas
Why does reactivity decrease going down group 7
Atomic radius increases
More inner shells so shielding increases
Less nuclear attraction to capture an electron from another species
Reactivity decreases
Trend in oxidising power
Oxidising power decreases down the group
Trend in reducing power
Reducing power increases down the group
What is disproportionation
A redox reaction in which the same element is both oxidised and reduced ]eg chloride +cold dilute sodium hydroxide
Write the disproportionation reaction for chlorine +water
Cl2 + H20= HClO + HCl
Benefits of caloric acid
Bacteria is killed by chloride 1 acid
And chlorate 1 ions
Also chloride acid acts as a weak bleach
Benefits and risks of chlorine use
Chlorine is a toxic gas
Chlorine is a respiratory irritant in small concentrations
In large concentrations it is fatal
Can form chlorinated hydrocarbons which are suspected carcinogens
Prevents the breakout of typhoid and cholera
Solubility of group 7
Solubility decreases down group 7
Describe the test for anions (carbonate test )
Add dilute nitric acid
If bubbles are seen carbonate ions are present
As the gas produced will be carbon dioxide
To prove it is co2 bubble the gas through lime water - calcium hydroxide +white precipitate of calcium carbonate will form turning the lime water cloudy
Describe the sulfate test
Add add excess barium nitrate or barium chloride
Barium and sulphate ions form a white precipitate
Ba 2+ +so42-= baso4 solid
Describe the halide test
Add silver nitrate to an aq solution of a halide
Chlorine white ppt
Bromine cream ppt
Iodine yellow ppt
Solubility of silver halides in ammonia
Cl - soluble in dilute ammonia
Br- soluble in conc ammonia
I - insoluble in conc ammonia
Sequence of tests
Carbonate test
Sulfate test baco3 is insoluble in water so there must be no carbonate present
Halide test silver carbonate an silver sulfate are bothe insoluble so this test use be carried out last
Mixture of ions in ion testing
Carbonate test - keep adding dilute nitric acid till bubbling stops
Sulfate test any sulfate ions will precipitate as barium sulfate filter solution to remove all barium sulfate
Halide test silver carbonate add silver nitrate and nH3 - ammonia t confirm halide
Test for ammonium - nh4
Heat - aqueous ammonium ions and hydroxide ion react to form ammonia gas
Add Naomi before heating damp litmus paper will turn it blue is ammonia gas is alkaline
