C3.4 Further analysis and quantitative chemistry

Question 1

Test for lithium?

Answer 1

a CRIMSON flame

Question 2

Test for sodium?

Answer 2

a YELLOW flame

Question 3

Test for potassium?

Answer 3

a LILAC flame

Question 4

Test for calcium?

Answer 4

a RED flame

or

forms a white precipitate in sodium hydroxide solution

Question 5

Test for barium?

Answer 5

a GREEN flame

Question 6

Test for aluminium?

Answer 6

Forms a white precipitate with sodium hydroxide solution and dissolves in excess sodium hydroxide solution

Question 7

What can flame tests be used to identify?

Answer 7

metal ions: Lithium, sodium, potassium, calcium, barium

compounds produce distinctive colours in flame tests

Question 8

Test for magnesium ions?

Answer 8

form white precipitates with sodium hydroxide solution

Question 9

Test for copper(II) ?

Answer 9

Forms blue precipitates with sodium hydroxide solution

Question 10

Test for iron(II)?

Answer 10

Forms a green precipitate with sodium hydroxide solution

Question 11

Test for iron(III) ?

Answer 11

Forms a brown precipitate with sodium hydroxide solution

Question 12

What colour precipitates do aluminium, calcium and magnesium form with sodium hydroxide solution?

Answer 12

White

Question 13

When carbonates react with dilute acids, what is formed?

Answer 13

carbon dioxide

Question 14

What is the test for carbon dioxide?

Answer 14

by bubbling it through limewater

produces white precipitates, causing lime water to turn cloudy if carbondioxide is present

Question 15

Acid + Carbonate———–

Answer 15

Salt + Water + Carbon Dioxide

Question 16

Halide ions in solution produce precipitates with…….

Answer 16

silver nitrate solution in the presence of dilute nitric acid

Question 17

Test for chloride ions?

Answer 17

Acidify with nitric acid

add silver nitrate solution

forms a white precipitate

Question 18

Test for bromide ions?

Answer 18

Acidify with nitric acid

add silver nitrate solution

forms a cream precipitate

Question 19

Test for iodide ions?

Answer 19

Acidify with nitric acid

add silver nitrate solution

forms a yellow precipitate

Question 20

Give examples of halide ions

Answer 20

chloride

bromide

iodide

Question 21

What chemicals are needed to test for halide ions?

Answer 21

silver nitrate solution and dilute nitric acid

Question 22

Test for sulfate ions?

Answer 22

a white precipitate is formed with dilute hydrochloric acid and barium chloride solution

Question 23

How can the volumes of acid and alkali solutions that react with each other be measured?

Answer 23

by titration using a suitable indicator

Question 24

What can titrations be used to do?

Answer 24

to find exactly how much acid is needed to neutralise quantity of alkali (or vice versa)

Question 25

What indicator is usually used in titrations?

Answer 25

phenolphthalein

Question 26

In titrations why do we use the indicator phenolphthalein instead of universal indicator?

Answer 26

As universal indicator changes colour gradually- we want a definite colour change

Question 27

Describe how to carry out titrations?

Answer 27

Put some alkali in the flask, along with some indicator- phenolphthalein Put acid into the burette until it reaches 0 dm3 Add the acid a bit at a time to the alkali using the burette, giving the flask a regular swirl. The indicator then changes colour when all the alkali has been neutralised. Record the amount pf acid used to neutralise the alkali repeat and calculate a mean

Question 28

In the equation n= c x V What do the letters stand for and what are the units?

Answer 28

n- number of moles c- concentration in mol/dm3 V- Volume dm3

Question 29

In the equation m = n X Mr What do the letters stand for and what are the units?

Answer 29

m- mass (g) n- number of moles Mr- Relative formula mass

Question 30

Suggest why it is difficult to identify potassium ions when sodium ions are present in flame tests

Answer 30

as lilac colour of potassium is obscured by yellow colour of sodium

Question 31

Describe how a student could confirm a salt contains magnesium ions and not aluminium ions

Answer 31

add excess sodium hydroxide solution with salt aluminium ions would dissolve

Question 32

Describe how a student could confirm a salt does not contain calcium ions

Answer 32

place sample in a flame (flame test) flame does not go red

Question 33

Test for carbonate ion?

Answer 33

carbon dioxide is produced in the presence of a dilute acid