analysis

Question 1

aluminium, calcium and magnesium ions

Answer 1

• form white precipitates
• with sodium hydroxide solution
• aluminium hydroxide precipitate dissolves in excess sodium hydroxide solution

Question 2

copper(2) , iron (2) , iron (3)

Answer 2

• form blue, green and brown respectively with sodium hydroxide solution

Question 3

carbonates

Answer 3

• react with dilute acids to form CO2

- co2 produces a white precipitate with limewater which turns cloudy

Question 4

flame tests

Answer 4

lithium - crimson
sodium- yellow
potasssium - lilac
calcium- red
barium - green

Question 5

halide ions

Answer 5

• in solution produce precipitates with solver nitrate solution in the presence of dilute nitric acid
• sliver chloride is white, silver bromide is cream and silver iodide is yellow

Question 6

sulfate ions

Answer 6

• in solution produce a white precipitate with barium chloride solution in the presence of dilute hydrochloric acid

Question 7

paper chromatography

Answer 7

• used to find whether a dye is made up of a single coloured substance or mixture
• soluble dyes spread along the paper faster and so the dyes separate
• base line should be drawn with pencil so that it does not dissolve in the solvent
• the solvent should be below base line to begin with
• a lid should be used to prevemt the solvent from evaporating
• different solvents can be used to maximise separation

Question 8

gas chromatography

Answer 8

• allows the separation of a mixture of compounds
• the time taken for a substance to travel through the column can be used to help identify the substance
• the output can be linked to a mass spectrometer, which can be used to identify the substances leaving the end of the column
• the mass spectrometer can also give the molecular mass of each of the substances separated in the column

Question 9

titration

Answer 9

• the volumes of acid and alkali solutions that react with eachother can be measured by titration using a suitable indicator
  1- wash biurette with water then the solution to be put in it
  2- fill the biurette
  3- clean a pipette with water and then with the solution that is going to be measured in it
  4- transfer 25cm(3) with the pipette into a clean connical flask
  5) add a few drops of suitable indicator
  6- place a white tile underneath to compare the colour change
  7- rough titration
  8- repeat
• if the concentration of one of the reactants is known the results of the titration can be used to find the concentration of the other reactant

Question 10

titration calculations

Answer 10

• calculate number of moles of acid using : n= cv
• work ou the number of moles of alkali using the chemical equation
• calculate the concentration of the alkali using n= cv
  c= n/v