C2a Topic 2 - Ionic Compounds and Analysis Flashcards
An ion is
An atom or group of atoms that have a charge
Ions form..
1) A closely packed regular lattice arrangement.
2) This is because ionic bonds are very strong electrostatic forces of attraction between oppositely charged ions.
3) This gives ionic compounds similar properties.
Ionic compounds share the following properties…
1) They have HIGH MELTING and BOILING POINTS - because of the very strong bonds between the ions. It takes a lot of energy to break these bonds.
2) The CONDUCT ELECTRICITY when MOLTEN or AQUEOUS - in an aqueous solution the ions separate and are all free to move, so they’ll carry electric current. The same happens when they melt - the ions are free to move and they’ll carry electric current.
When 2 different elements combine the compound’s name is
‘something -IDE’
When 3 or more different elements combine and one of them is OXYGEN, the compound’s name is often
‘something -ATE’
Common salts of sodium, potassium and ammonium are
Soluble!
Nitrates are
Soluble!
Common chlorides are
Soluble (except silver chloride and lead chloride)
Common sulphates are
Soluble (except lead, barium and calcium sulphate)
Common carbonates and hydroxides are
Insoluble (except for sodium, potassium and ammonium ones)
To make insoluble salts, we use __________ reactions
Precipitation
Barium sulphate
Is an insoluble salt!
Describe how you would make a pure, dry sample of barium sulphate
1) Mix solutions of barium nitrate and potassium sulphate (you want a soluble salt of barium “something”, and a soluble salt of “something” sulphate).
2) Filter out the precipitate of barium sulphate.
3) Wash it with distilled water.
4) Dry it on filter paper.
Why is barium sulphate so useful
1) It is opaque to X-rays. When drunk it shows up the gut so that any problems can be seen.
2) Barium salts are toxic, but barium sulphate can be safely drunk because it’s insoluble. This means it isn’t absorbed into the bloodstream - it just passes through the body.
Sodium ions produce a _________ flame
Yellow/orange
Potassium ions produce a __________ flame
Lilac
Calcium ions give a _________ ______ flame
Brick red
Copper ions give a _______/_________ flame
Blue/green
Flame tests work when you have
A sample of a pure element AND ALSO if you have a compound that contains that element!
How should you clean the wire loop when doing flame tests
By dipping it in Hydrochloric acid and rinsing it with distilled water
How can we test for Carbonates
1) Test for Carbon dioxide. You can do this by bubbling the gas through limewater. If the gas is carbon dioxide, the limewater turns cloudy!
2) This works because in a CASHOCO reaction carbonates react with dilute acids to form a salt + water + carbon dioxide!
How can we test for Sulphates
1) Add dilute Hydrochloric acid, followed by barium chloride solution!
2) A white precipitate of barium sulphate means the original compound was a sulphate.
How do we test for Chlorides
1) Add dilute nitric acid followed by silver nitrate solution!
2) A chloride gives a white precipitate of silver chloride!
What method can we use to identify elements FOR CERTAIN
Spectroscopy
Which groups are most likely to form ions
Groups 1&2 and 6&7
