Chemical Analysis

Question 1

State the colour for the flame test of a Lithium Ion (Li⁺)

Answer 1

Crimson/red

Question 2

State the colour for the flame test of a Sodium Ion (Na⁺)

Answer 2

Orange

Question 3

State the colour for the flame test of a Potassium Ion (K⁺)

Answer 3

Lilac/Purple

Question 4

State the colour for the flame test of a calcium ion (Ca²⁺)

Answer 4

Red

Question 5

State the colour for the flame test of a Barium Ion (Ba²⁺)

Answer 5

Green

Question 6

State the observation when a few drops of sodium hydroxide is added to iron (II) chloride

Answer 6

green precipitate/solid

Question 7

State the observation when a few drops of sodium hydroxide is added to iron (III) chloride

Answer 7

brown precipitate/solid

Question 8

State the colour for the flame test of a Lithium Ion (Li+)

Answer 8

Crimson/red

Question 9

State the colour for the flame test of a Sodium Ion (Na+)

Answer 9

Orange

Question 10

State the colour for the flame test of a Potassium Ion (K+)

Answer 10

Lilac/Purple

Question 11

State the colour for the flame test of a calcium ion (Ca2+)

Answer 11

red

Question 12

State the colour for the flame test of a Barium Ion (Ba2+)

Answer 12

Green

Question 13

State the observation when a few drops of sodium hydroxide is added to iron (II) chloride

Answer 13

green precipitate/solid

Question 14

State the observation when a few drops of sodium hydroxide is added to iron (III) chloride

Answer 14

brown precipitate/solid

Question 15

State the observation when a few drops of sodium hydroxide is added to copper chloride

Answer 15

blue precipitate/solid

Question 16

State the observation when a few drops of sodiurecipitate/solidm hydroxide is added to calcium chloride

Answer 16

white precipitate/solid

Question 17

State the observation when a few drops of sodium hydroxide is added to magnesium chloride

Answer 17

white precipitate/solid

Question 18

State the observation when a few drops of sodium hydroxide is added to aluminium chloride

Answer 18

white precipitate/solid

Question 19

State the observation when an excess of sodium hydroxide is added to aluminium chloride

Answer 19

precipitate dissolves/disappears

Question 20

Describe how to distinguish between calcium and magnesium ions

Answer 20

flame testcalcium ions give a red flame

Question 21

Describe the test for carbonate ions

Answer 21

Add an acidBubblesof carbon dioxidewhich turns limewater cloudy

Question 22

Describe the test for sulphate ions

Answer 22

Add acidified barium chloride makes a white precipitate (solid)

Question 23

Describe the test for chloride ions

Answer 23

Add silver nitrate makes a white precipitate (solid)

Question 24

Describe the test for bromide ions

Answer 24

Add silver nitrate makes a cream precipitate (solid)

Question 25

Describe the test for iodide ions

Answer 25

Add silver nitrate makes a yellow precipitate

Question 26

Give two advantages of using instrumental methods of analysis. [1]

Answer 26

faster more sensitive more accurate can detect smaller amounts

Question 27

Name the precipitate made when acidified barium chloride is added to sodium sulfate

Answer 27

barium sulfate BaSO₄

Question 28

Name the precipitate made when silver nitrate is added to potassium chloride

Answer 28

silver chloride AgCl

Question 29

Name the precipitate made when silver nitrate is added to potassium bromide

Answer 29

silver bromide AgBr

Question 30

Name the precipitate made when silver nitrate is added to potassium iodide

Answer 30

silver iodide AgI

Question 31

Describe the test for hydrogen

Answer 31

Burn it makes a squeaky pop

Question 32

Describe the test for oxygen

Answer 32

Relights a glowing spill

Question 33

Describe the test for chlorine gas

Answer 33

Bleaches blue litmus paper

Question 34

Describe the test for carbon dioxide

Answer 34

turns limewater cloudy

Question 35

Explain why carbon dioxide turns limewater cloudy

Answer 35

Calcium hydroxide reacts with carbon dioxide to form calcium carbonate Ca(OH)_2(aq) + CO_2(g) --\> CaCO_3(s) + H₂O_(l)

Question 36

Describe a limitation of flame tests

Answer 36

Can't analyse mixtures as one colour masks others

Question 37

Describe a disadvantage of chromatography

Answer 37

Similar substances have similar Rf values Needs a reference to compare to

Question 38

Describe how to carry out paper chromatography

Answer 38

Draw a pencil line about 1cm up the paper Place a small spot of the substance onto the paper Suspend the paper so that the bottom just touches the solvent

Question 39

Answer 39

Water level is above the start line Colours would dissolve

Question 40

Answer 40

Calcium **ions** sodium **ions** **(note the word ion is required for the mark)**

Question 41

Calculate the Rf value of W

Answer 41

Rf = distance travelled by substance ÷ distance travelled by solvent = 3 ÷ 10 = 0.3 (note Rf values are **always** less than 1)

Question 42

From the chromatogram, what conclusions can the scientist make about the colourings in sweets S and P?

Answer 42

* S contains six / 6 colourings * P contains five / 5 colourings if neither of first 2 bullet points given allow 1 mark for S contains more colours than P or converse • both S and P contain the same five / 5 colourings * both contain W and Y * both sweets (may) cause hyperactivity ignore unsafe • neither contain X and Z