C8 - Chemical Analysis

Question 1

what is a pure substance

Answer 1

a single element or compound not mixed with any other substance

Question 2

what can be used to distinguish pure substances from mixtures

Answer 2

melting and boiling point data

Question 3

what is a formulation

Answer 3

a mixture that has been designed as a useful product

Question 4

how are formulations made

Answer 4

mixing the components in carefully measured quantities to ensure the product has the required properties

Question 5

give examples of formulations

Answer 5

fuels
cleaning agents
paints
medicines
alloys
fertilisers
food

Question 6

formula to calculate rF value

Answer 6

distance moved by substance/ distance moved by solvent

Question 7

what may affect the rF value

Answer 7

the solvent

Question 7

what is the test for hydrogen

Answer 7

using a burning splint held at the open end of a test tube of gas. hydrogen makes a pop sound and burns

Question 7

how can a chromotogram be used to identify substances by comparing them with known substances

Answer 7

the number of spots they produce and the colour
how far the spots have moved up the paper or have the same Rf value

Question 8

oxygen test

Answer 8

using a glowing splint inserted into a test tube of the gas. the splint relights in oxygen

Question 9

carbon dioxide test

Answer 9

using an aqueous solution calcium hydroxide. carbon dioxide when shakened or bubbled through will turn the limewater milky

Question 10

chlorine test

Answer 10

if damp litmus paper is put onto chlorine gas it is bleached

Question 11

what can flame tests be used to identify

Answer 11

some metal ions

Question 12

what colour do lithium compounds turn in the flame test

Answer 12

crimson flame

Question 13

what colour do sodium compounds turn in the flame test

Answer 13

yellow flame

Question 14

what colour do potassium compounds turn in the flame test

Answer 14

lilac flame

Question 15

what colour do calcium compounds turn in the flame test

Answer 15

an orange-red flame

Question 16

what colour do copper compounds turn in the flame test

Answer 16

green flame

Question 17

what can be done if a sample contains a mixture of ions

Answer 17

some flame colours can be masked

Question 18

what can sodium hydroxide solution be used to identify

Answer 18

some metal ions

Question 19

which ions form white precipitates when added to sodium hydroxide

Answer 19

aluminium (but then redissolves in excess NaOH to form a colourless solution), calcium and magnesium ions

Question 20

what ions form coloured precipitates when added to sodium hydroxide

Answer 20

copper ii, iron ii, iron iii

Question 21

what colour does copper ii form when added to sodium hydroxide

Answer 21

blue precipitate

Question 22

what colour do iron ii ions form when added to sodium hydroxide

Answer 22

green precipitate

Question 23

what colour do iron iii ions form when added to sodium hydroxide

Answer 23

brown precipitate

Question 24

balanced equation to represent calcium reacting with insoluble hydroxide

Answer 24

Ca2+ + 2OH- ------> Ca(OH)2

Question 25

balanced equation to represent copper ii reacting with insoluble hydroxides

Answer 25

Cu2+ + 2OH- ----> 20

Question 26

balanced equation to represent iron ii reacting with insoluble hydroxides

Answer 26

Fe2+ + 2OH- ---> Fe(OH)2

Question 27

balanced equation to represent iron iii reacting with insoluble hydroxides

Answer 27

Fe3+ + 3OH- ------> Fe(OH)3

Question 28

balanced equation to represent alumminium reacting with insoluble hydroxides

Answer 28

Al3+ + 3OH- ---> Al(OH)3

Question 29

balanced equation to represent magnesium reacting with insoluble hydroxides

Answer 29

Mg2+ + 2OH- ---> Mg(OH)2

Question 30

what do carbonates to react with to form carbon dioxide gas

Answer 30

dilute acids

Question 31

what can CO2 be identified with

Answer 31

limewater

Question 32

what do halide ions produce and when

Answer 32

precipitates with silver nitrate when there is dilute nitirc acid

Question 33

what colour precipitate is silver chloride

Answer 33

white

Question 34

what colour precipitate is silver bromide

Answer 34

cream

Question 35

what colour is silver iodide

Answer 35

yellow

Question 36

what do sulfate ions produce

Answer 36

white precipitate with barium chloride solution in the presence of hydrochloric acid

Question 37

what can be detected using instrumental methods

Answer 37

elements and compounds

Question 38

benefits of instrumental methods

Answer 38

accurate sensitive rapid can be used to identify ions in mixtures

Question 39

how does flame emission spectroscopy work

Answer 39

the sample is put into a flame and the light given out is passed through a spectroscope. the output is a line spectrum that can be analysed to identify the metal ions in the solution and measure their concentrations