chemical analysis

Question 1

lithium ion

Answer 1

crimson flame

Question 2

sodium ion

Answer 2

yellow flame

Question 3

potassium ion

Answer 3

lilac flame

Question 4

calcium ion

Answer 4

orange-red flame

Question 5

copper ion

Answer 5

green flame

Question 6

what are the problems of using flame tests

Answer 6

the colour of a flame test can be difficult to distinguish, that is especially true if there is only a low concentration of of the metal compound
sometimes a sample contains a mixture of metal ions which can mask the colour of the flame

Question 8

what is flame emission spectroscopy

Answer 8

a sample of the metal ion in solution is placed into a flame , the light given ute is passed into a machine called a spectroscope, the spectroscope converts the light into a line spectrum
the positions of the lines in the spectrum are specific for a given metal ion

Question 9

what are advantages to instrumental methods

Answer 9

they are rapid, we could use flame emission spectroscopy to analyse samples quicker than using flame tests
they are sensitive flame emission spectroscopy will work even on y sample of metal compound
they are accurate flame emission spectroscopy is more likely to identify a metal ion correctly than using a flame test

Question 10

how do calcium ions react with sodium hydroxide solution

Answer 10

form a white precipitate

Question 11

how do magnesium ions react with sodium hydroxide solution

Answer 11

form a white precipitate

Question 12

how do aluminium ions react with sodium hydroxide

Answer 12

form a white precipitate

Question 13

how can you identify aluminium ions in the white precipitate

Answer 13

if you add excess sodium hydroxide solution the aluminium precipitate redissolves, turning clear

Question 14

how do you identify calcium ions in the white precipitate

Answer 14

flame tests

Question 15

how do copper II ions react with sodium hydroxide

Answer 15

form a blue precipitate of copper (II) hydroxide

Question 16

how do iron (II) ions react with sodium hydroxide solution

Answer 16

form a green precipitate of iron (II) hydroxide

Question 17

how do iron (III) ions react with sodium hydroxide solution

Answer 17

they form a brown precipitate of iron (III) hydroxide

Question 18

how do identify carbonate ion

Answer 18

1. add dilute acid to our sample
2. the acid will react with the carbonate to make carbon dioxide gas, we will see effervescence (fizzing.)
3. bubble the gas through lime water if the water goes cloudy this proves we have carbon dioxide which means we started with the carbonate ion

Question 19

how to test for halide ion (chloride, bromide and iodide)

Answer 19

1. add dilute nitric acid to the sample
2. add dilute silver nitrate solution
3. halide ions produce a precipitate of the silver halide. Each halide makes a different coloured precipitate
   chloride- white precipitate of silver chloride, bromide- cream precipitate of silver bromide, iodide- yellow precipitate of silver iodide

Question 20

how to test for sulfate ions

Answer 20

1. add dilute hydrochloric acid to our sample
2. add barium chloride solution
3. if sulfate ions are present we will see a white precipitate