C8

Question 1

What is a pure substance?

Answer 1

A single element or compound, not mixed with any other substance

Question 2

What is a formulation?

Answer 2

A mixture designed as a useful product

Question 3

What are some examples of formulations?

Answer 3

Fuels; cleaning agents; paints; medicines; alloys; fertilisers and foods

Question 4

What can chromatography be used for?

Answer 4

To separate mixtures and can give information to help identify substances.

Question 5

What is the stationary phase in chromatography?

Answer 5

Chromatography paper

Question 6

What is the mobile phase in chromatography?

Answer 6

The solvent (that travels up the paper)

Question 7

What’s the equation to work out the Rf value?

Answer 7

distance moved by substance / distance moved by solvent. Always between 0 and 1

Question 8

How to do chromatography?

Answer 8

1. Draw a pencil line about 1cm from the bottom of the paper. 2. Add ink spots to the line. 3. Place the paper in a solvent but the dots must be above the solvent. 4.Allow solvent to move up the paper. 5. Leave to dry and measure distance the ink and solvent travelled to work out the Rf value.

Question 9

What is the test and positive result for hydrogen?

Answer 9

Put a lit splint near the gas. Squeaky pop occurs.

Question 10

What is the test and positive result for oxygen?

Answer 10

Glowing splint relights if oxygen is present.

Question 11

What is the test and positive result for carbon dioxide?

Answer 11

Lime water goes cloudy / milky.

Question 12

What is the test and positive result for chlorine?

Answer 12

DAMP litmus paper is bleached / turns white.

Question 13

What can flame tests identify?

Answer 13

Some metal ions.

Question 14

What flame is visible for lithium ions?

Answer 14

Crimson

Question 15

What flame is visible for calcium ions?

Answer 15

Red / orange

Question 16

What flame is visible for sodium ions?

Answer 16

Yellow

Question 17

What flame is visible for copper ions?

Answer 17

Green

Question 18

What flame is visible for potassium ions?

Answer 18

Lilac

Question 19

What happens if there is a mixture of ions?

Answer 19

Some may be masked and not seen.

Question 20

How can you identify some metal ions (cations)?

Answer 20

Add sodium hydroxide solution

Question 21

Once you’ve added sodium hydroxide; which ions form white precipitate and what are the equations?

Answer 21

Aluminium - Al3+ + 3OH- —> Al(OH)3. Aluminium dissolves though in excess solution! Calcium - Ca2+ + 2OH- –> Ca(OH)2. Magnesium - Mg2+ +2OH- —> Mg(OH)2

Question 22

Once you’ve added sodium hydroxide; which ion forms blue precipitate and what is the equation?

Answer 22

Copper II - Cu2+ + 2OH- —> Cu(OH)2

Question 23

Once you’ve added sodium hydroxide; which ion forms green precipitate and what is the equation?

Answer 23

Iron II - Fe2+ + 2OH- —> Fe(OH)2

Question 24

Once you’ve added sodium hydroxide; which ion forms brown precipitate?

Answer 24

Iron III - Fe3+ + 3OH- —> Fe (OH)3

Question 25

What do carbonates and dilute acids form once they've reacted?

Answer 25

Carbon dioxide. Check with limewater test.

Question 26

What do you add to identify a halide ion?

Answer 26

Add a few drops of dilute nitric acid and silver nitrate solution

Question 27

What are the results for halide ions?

Answer 27

Chloride ---> white precipitate of silver chloride. bromide ---> cream precipitate of silver bromide. Iodide ---> yellow precipitate of silver iodide.

Question 28

How do you identify sulfate ions?

Answer 28

Add a few drops of HCl to solution and then a few drops of Barium Chloride solution - a white precipitate of barium sulphate should form.

Question 29

How can elements and compounds detected and identified and why this?

Answer 29

Instrumental methods because they are accurate sensitive and rapid.

Question 30

What is an example an instrumental method?

Answer 30

Flame emission spectroscopy - analyses metal ions.

Question 31

How does flame emission spectroscopy work?

Answer 31

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.