C12

Question 1

What is a pure substance?

Answer 1

A substance made from one type of element or compound

Question 2

What is a mixture?

Answer 2

A substance made from two+ DIFFERENT elements or compounds that are not chemically combined

Question 3

What is a formulation?

Answer 3

A mixture that has been specifically designed for a useful product

Question 4

If a small is pure, will it have a small or large range of boiling/melting point?

Answer 4

Small

Question 5

Name 2 ways the bp and mp of a substance can be used to tell if its pure or not

Answer 5

• looking at range
• comparing results to a database

Question 6

What is the test for hydrogen?

Answer 6

Hold a lit splint near sample, hydrogen will burn with a squeaky pop

Question 7

What is the test for oxygen?

Answer 7

Hold glowing splint near sample, splint will relight if oxygen is present

Question 8

What is the test for carbon dioxide?

Answer 8

Turns limewater clear to cloudy

Question 9

What is the test for chlorine?

Answer 9

Turns damp blue litmus paper white

Question 10

In paper chromatography, what is the mobile phase?

Answer 10

A solvent such as water

Question 11

If a compound is more strongly attracted to the mobile phase than the stationary phase, it will _____

Answer 11

Travel further up the paper

Question 12

Why is the baseline drawn in pencil not ink?

Answer 12

Ink will dissolve

Question 13

How do you calculate Rf?

Answer 13

Substance travelled by substance/substance travelled by solvent

Question 14

How many spots will a pure substance produce?

Answer 14

1

Question 15

How can you identify an unknown compound in paper chromatography?

Answer 15

Find the Rf then compare it to known substances in a database
Or
Include known samples and see if any spots travel the same distance

Question 16

How might you carry out a flame test for metal ions?

Answer 16

• dip a nichrome wire loop into a concentrated hydrochloric acid and then heat it to sterilise
• dip the wire into the unknown sample, then hold it in a roaring flame on a Bunsen burner
• the colour of the flame tells you if certain metal ions are present

Question 17

What colour flame will sodium produce?

Answer 17

Yellow

Question 18

Which metal ion produces a green flame?

Answer 18

Copper

Question 19

What colour flame does potassium produce?

Answer 19

Lilac

Question 20

Which metal ion produces a crimson flame?

Answer 20

Lithium

Question 21

What colour flame does calcium produce?

Answer 21

Orange-red

Question 22

To test for carbonate ions, add ___. If ____ is observed, carbonate ions are present.

Answer 22

Dilute acid, fizzing

Question 23

___ + acid —-> salt + ____ + _____

Answer 23

Metal carbonate
Water
Carbon dioxide

Question 24

____ solution can be used to identify some metal ions

Answer 24

sodium hydroxide

Question 25

which ions form a white precipitate with sodium hydroxide solution?

Answer 25

- Al3+ - Ca2+ - Mg2+ These ions react with sodium hydroxide to produce insoluble metal hydroxides

Question 26

how can you tell the 3 ions apart?

Answer 26

add more NaOH solution- aluminium precipitate will dissolve, but Ca and Mg precipitates won't You can then use a flame test to distinguish between Ca or Mg- Mg has no flame colour

Question 27

What colour precipitate does Cu2+ form?

Answer 27

blue

Question 28

What colour precipitate does Fe2+ form?

Answer 28

green

Question 29

What colour precipitate does Fe3+ form?

Answer 29

brown

Question 30

To test for halides, add ___ and then ___ solution. If a precipitate forms, a halide ion is present

Answer 30

- dilute nitric acid - silver nitrate

Question 31

chloride ions form which colour precipitate?

Answer 31

white

Question 32

bromide ions form which colour precipitate?

Answer 32

cream

Question 33

iodide ions form which colour precipitate?

Answer 33

yellow

Question 34

What are some positives of using modern equipment?

Answer 34

accurate, sensitive, quick, can work on small samples but EXPENSIVE

Question 35

Give an example of and explain an instrumental analysis

Answer 35

Flame emission spectroscopy: - metal ions emit unique wavelengths of light when they are heated - a spectrometer analyses the unique pattern of radiation from a heated sample and compares it to other known line spectra

Question 36

To test for sulfates, add ___ and then ___ solution.

Answer 36

- dilute hydrochloric acid - barium chloride

Question 37

In testing for sulfates, if a ___ forms, sulfate ions are present

Answer 37

white precipitate

Question 38

Why is hydrochloric acid added when testing for sulfates?

Answer 38

To remove any carbonate ions which would form a precipitate with the barium ions