Chemical Analysis

Question 1

What is a pure substance

Answer 1

A substance made from one single element or compound

Question 2

How can you tell if a substance is pure

Answer 2

It’s melts at a specific fixed temperature and has a fixed boiling point

Question 3

What’s the properties of impure substances 

Answer 3

They melt and boil over a range of temperatures

Question 4

What is a formulation

Answer 4

A mixture that has been designed as a useful product

Question 5

How’s a formulation made

Answer 5

The quantity of each component is carefully measured so that the product has the properties you need

Question 6

What is paper chromatography used for

Answer 6

To separate mixtures 

Question 7

What is the stationary phase in paper chromatography

Answer 7

The paper because it doesn’t move

Question 8

What is the mobile phase in paper chromatography

Answer 8

The solvent

Question 9

How can you tell if a substance is pure in paper chromatography

Answer 9

It will produce a single spot

Question 10

Why is the starting line drawn in pencil

Answer 10

To prevent it from dissolving in the solvent

Question 11

What can the Rf value be used for

Answer 11

To identify a substance

Question 12

How do you calculate the Rf value

Answer 12

Distance moved by substance / Distance moved by solvent

Question 13

How do you perform a flame test

Answer 13

Placed a small amount of chemical onto wire mounted in a handle
Place wire into blue flame
The colour of the flame will show which metal ion is present

Question 14

What colour flame does lithium produce

Answer 14

Crimson flame 

Question 15

What colour flame does sodium produce

Answer 15

Yellow flame

Question 16

What colour flame does potassium produce 

Answer 16

Lilac flame

Question 17

What colour frame does calcium produce

Answer 17

Orange-red flame

Question 18

What colour frame does copper produce

Answer 18

Green flame 

Question 19

What’s the disadvantages of using flame tests

Answer 19

• Colour of the flame can be difficult to distinguish
• Samples can contain a mixture of metal ions

Question 20

How do you carry out flame emission spectroscopy 

Answer 20

A sample of metal is placed in a flame
The light given out is then passed into a spectroscope 
The spectroscope converts the light into a line spectrum

Question 21

What is flame emission spectroscopy an example of

Answer 21

An instrumental method

Question 22

What are features of instrumental methods of analysis

Answer 22

Rapid sensitive and accurate

Question 23

Which three metals form white precipitate in sodium hydroxide

Answer 23

Sodium magnesium and aluminium

Question 24

Which metal redissolves In excess sodium hydroxide

Answer 24

Aluminium

Question 25

Copper reacts with sodium hydroxide to form what colour precipitate

Answer 25

A blue precipitate

Question 26

Iron (Fe 2+) reacts with sodium hydroxide to form what precipitate 

Answer 26

Green precipitate

Question 27

Iron (Fe 3+) reacts with sodium hydroxide to form what precipitate

Answer 27

A brown precipitate

Question 28

What is the method for testing for the carbonate ion

Answer 28

Add dilute acid to the sample The acid will react with the carbonate to form carbon dioxide Bubble the gas through limewater if it goes cloudy then carbon dioxide is present which proves that the carbonate ion was present

Question 29

How do you test for the halide ion

Answer 29

Add nitric acid to the sample Add dilute silver nitrate solution The halide ions will produce a precipitate

Question 30

What colour precipitate does Chloride ions form

Answer 30

White

Question 31

What colour precipitate do bromide ions form

Answer 31

Cream

Question 32

What colour precipitate do iodide ions produce

Answer 32

Yellow precipitate

Question 33

How do you test for sulphate ions

Answer 33

Add hydrochloric acid add barium chloride if sulphate is present we will see a white precipitate