Chapter 8 Flashcards
(14 cards)
What happens to the solubility of hydroxides as you go down a group?
As you go down, the solubility decreases.
The pH increases.
Alkalinity increases
Why do group 2 elements become more reactive as you go down?
As you go down:
Total ionisation energies decrease as the nuclear attraction on outer electron decrease due to increased atomic radius and increased shielding.
Becomes easier to remove electron and reactivity increases.
What are the uses of group 2 compounds as bases
Used in agriculture
Used in medicine
Experiment to show trend in solubility down group 2
Add a spatula of each group 2 oxide in water
Shake the mixture and wait for precipitate to form at bottom
Measure pH and Allan it’s will increase down the group
What happens as you go down group 17?
More electrons
Stronger London forces
More energy required to break the intermolecular forces
Boiling point increases
They are diatomic molecules with covalent bonds between atoms.
Molecules are non-polar so there are London forces only between molecules.
Halogen molecules have more electrons as you go down group 17, so have larger London forces.
Appearance of the halogen molecule at RTP
Fluorine- pale yellow gas
Chlorine- pale green gas
Bromine- red-brown liquid
Iodine- shiny grey-black solid
Astatine- never been seen
Trend in reactivity as you go down group 17
Atomic radius increases
More inner shells so shielding increase
Less nuclear attraction to capture an electron from another species
Reactivity decreases
What is disproportionation?
It is a redox reaction in which the same element is both oxidised and reduced.r
Benefits of chlorine use
Ensures that bacteria is killed
Risks of chlorine use
Toxic gas
Respiratory irritant
Can cause cancer
How to test for carbonate ions?
Add dilute nitric acid to solid
If you see bubbles, the unknown compound is a carbonate
Proof for co2- bubble through limewater and will turn cloudy
How to test for sulfate?
Formation of white precipitate
Aqueous barium ions are added to a solution of an unknown compound
How to test for halides?
Add aqueous silver nitrate, AgNO3, to an aqueous soliton of halide
Silver halide precipitates are different colours
Silver chloride- white
Silver bromide-cream
Silver iodide- yellow
Add aqueous ammonia to test for solubility of precipitate. Useful as colours can be difficult to tell.
How to test for solubility?
Chloride- soluble in dilute NH3
Bromide- soluble in concentrated NH3
Iodide- insoluble in concentrated NH3
