C2a Topic 2

Question 1

Ionic bonding

Answer 1

• transfer the electrons from positively or negatively charged atoms called ions.
• atoms that have one or two electrons in their outer shells want to get rid of them so they can have a full shell. They are cations.
• atoms that have a nearly full outer shell need to gain an electron so they can have a full shell. they are anions as they gained electrons
• when they join they form ionic bonds

Question 2

ionic compounds

Answer 2

• dot and cross diagrams
• have a regular lattice structure - the ions form a closely packed lattice structure because ionic binds are very strong forces between opposite charged ions
• ionic compounds have similar properties because of this
  • high melting and boiling points - takes a lot of energy to break the strong bonds
  • conduct electricity when aqueous or molten - ions separate in an solution allowing them to move freely and carry electric current - same when they melt

Question 3

preparing insoluble salts

Answer 3

• soluble or insoluble
  • common salts of potassium, sodium and ammonium - soluble
  • nitrates - soluble
  • common chlorides - soluble ( except silver and lead chlorides)
  • common sulfates - soluble (except for lead, barium and calcium sulfate)
  • common carbonates and hydroxides - insoluble (except for sodium, pottasium and ammonium ones)
• making insoluble salts - precipitate reactions
  you have to mix two soluble salts
  1- add a spatula of lead nitrate to a test tube and fill with distilled water. make sure it is dissolved. then do the same with a spatula of sodium chloride
  2- mix in a beaker and the lead should become a precipitate
  3- pour the contents of the beaker through filter paper, make sure you get all the product from the beaker
  4- rinse the contents of the filter paper with distilled water to make sure all the soluble sodium nitrate has been washed away. you’ll be left with an insoluble - lead chloride

Question 4

barium meals

Answer 4

how to make a sample of barium sulfate (example of insoluble salt)
1- mix solution of barium nitrate and potassium sulfate
2- filter out the precipitate of barium sulfate
3- wash with distilled water
4- dry on filter paper
Can be used for x-rays
- when drunk, it shows up the gut to show any problems
- are toxic but is insoluble so can’t be absorbed into the bloodstream

Question 5

flame tests

Answer 5

sodium - yellow/orange flame
potassium - lilac
calcium - red
copper - blue/green

Question 6

testing for negative ions

Answer 6

• carbonates - CO2
  bubbling lime water - present = milky
• sulfate iobs
  ADD dilute HCl and barium chloride solution - white precipitate forms = original compound was a sulfate.
• chloride ions
  add dilute nitric acid followed by silver nitrate solution - chloride gives a white precipitate of silver chloride