Separation and Identification *

Question 1

What type of mixtures are filtration used for?

Answer 1

mixture of insoluble solid with a liquid or solution
mixture of solids suspended in gases

Question 2

What is an example of filtration?

Answer 2

separating sand from salty water

Question 3

What type of mixture is crystallisation used for?

Answer 3

mixture of a soluble solid with a liquid

Question 4

What is an example of crystallisation?

Answer 4

copper sulphate crystals from copper sulphate solution

Question 5

What type of mixtures are simple distillation used for?

Answer 5

mixture of 2 miscible liquids with a large difference in boiling point
mixture of a soluble solid with a solvent

Question 6

What is an example of simple distillation?

Answer 6

pure water from and ink and water mixture

Question 7

What type of mixtures are fractional distillation used for?

Answer 7

mixture of two or more miscible liquids with different boiling points
mixture of a soluble solid with a solvent

Question 8

What is an example of fractional distillation?

Answer 8

separating crude oil into separate groups of hydrocarbons of similar molecular size

Question 9

What type of mixture is paper chromatography used for?

Answer 9

a mixture of soluble dyes or inks

Question 10

What is an example of paper chromatography?

Answer 10

separating different dyes in an ink

Question 11

What is the test to identify hydrogen and what shows a positive result?

Answer 11

• add magnesium ribbon to test tube
• add 2cm of HCl and cover top with another test tube
• put lit splint into top test tube

squeaky pop

Question 12

What is the test to identify oxygen and what shows a positive result?

Answer 12

• add magnese oxide to test tube
• add 2cm of hydrogen peroxide
• cover top with another test tube
• blow out a lit splint and put it in the top test tube

the splint will relight

Question 13

What is the test to identify carbon dioxide and what shows a positive result?

Answer 13

• add marble chips to a boiling tube
• 2cm of limewater in test tube
• add 2cm of HCl to boiling tube
• put bung in boiling tube with the end in the limewater

limewater turns cloudy

Question 14

What is the test to identify ammonia and what shows a positive result?

Answer 14

damp red litmus paper

turns blue

Question 15

What is the test to identify chlorine and what shows a positive result?

Answer 15

damp blue litmus paper

turns red then bleaches

Question 16

How do you test for positive ions with sodium hydroxide solution?

What happens to each salt solution :

Iron sulphate
Iron chloride
Copper chloride
Aluminium salt solution
Calcium chloride
Ammonium hydroxide

Answer 16

• add the salt solution to test tube
• add sodium hydroxide drop by drop
• swirl after each drop
• if no precipitate is formed test for ammonia using damp red litmus paper

iron sulphate - dark green precipitate
iron chloride - orange/brown precipitate
copper chloride - green/blue precipitate
aluminium salt - white precipitate and dissolves
calcium chloride - white precipitate and dissolves
ammonium hydroxide - damp red litmus paper turns blue

Question 17

What is a precipitate?

Answer 17

an insoluble solid formed in a reaction involving gases or liquids

Question 18

What colour flame do these substances produce:

lithium chloride
sodium chloride
potassium chloride
calcium chloride
copper sulfate

Answer 18

lithium chloride - red/pink
sodium chloride - orange
potassium chloride - lilac
calcium chloride - orange/red
copper sulfate - blue/green

Question 19

What is a flame photometer?

Answer 19

an instrument used to identify metal ions and work out the concentration of metal ions in a solution

Question 20

How do you test for negative ions (carbonates)?

What type of reaction is this?

Answer 20

• add dilute HCl to the substance
• carbonates fizz because they give off carbon dioxide
• carry out the limewater test :
  
  • suck up carbon dioxide using a pipette
  • bubble through limewater
  • lime water turns cloudy is carbon dioxide is present

neutralisation reaction

Question 21

How do you test for negative ions (sulphates)?

What type of reaction is this?

Answer 21

• dissolve sulphate in distilled water
• add dilute HCl to solution
• add 2cm of this solution to a test tube
• add barium chloride solution drop by drop
• dense white precipitate will form

precipitation reaction

Question 22

How do you test for a halide (Cl, Br, I)?

What colour precipitate forms for each halide?

What kind of reaction is this?

Answer 22

• dissolve halide in distilled water
• add 2cm of halide solution to a test tube
• add a few drops of nitric acid
• add 6-12 drops of silver nitrate solution
• precipitate will form

chloride - white precipitate
bromide - cream precipitate
iodide - yellow precipitate

precipitation reaction

Question 23

Why do we use distilled water?

Answer 23

it has no ions which could cause a false positive