4.8.3☁️

Question 1

What are flame tests used for?

Answer 1

To identify some metal ions.

Question 2

What is the flame test for lithium?

Answer 2

Crimson

Question 3

What is the flame test for sodium?

Answer 3

Yellow flame

Question 4

What is the flame test for potassium?

Answer 4

Lilac flame.

Question 5

What is the flame test for calcium?

Answer 5

Orange-red flame.

Question 6

What is the flame test for copper?

Answer 6

Green flame.

Question 7

Why might using a flame test be ineffective?

Answer 7

A sample containing a mixture of metal ions would be hard to identify / distinguish as the flame colours can mask each other.

Question 8

What solution is added to identify metals?

Answer 8

Sodium hydroxide.

Question 9

What 3 metals can sodium hydroxide be used to identify?

Answer 9

Aluminium, calcium and magnesium.

Question 10

What colour precipitates to these form?

Answer 10

White

Question 11

What happens to the aluminium hydroxide precipitate in excess sodium hydroxide?

Answer 11

It dissolves.

Question 12

What colour precipitate does copper 2 form?

Answer 12

A blue precipitate.

Question 13

What colour precipitate does iron 2 produce?

Answer 13

A green precipitate.

Question 14

What colour precipitate does iron 3 form?

Answer 14

A brown precipitate.

Question 15

When forming an equation for the reactions of the reactions to produce insoluble hydroxides, what do you do?

Answer 15

You need as many hydroxide ions as the charge of the metal ions.

Question 16

What happens to the sodium from sodium hydroxide and the metal ion?

Answer 16

They react to form a compound.

Question 17

What is the test and result for carbonates?

Answer 17

Carbonates react with dilute acids to form carbon dioxide gases. Carbon dioxide gas can be identified with limewater.

Question 18

How do you test for halides?

Answer 18

You use dilute nitric acid with silver nitrate solution.

Question 19

What are 3 examples of halides and what precipitate do they form?

Answer 19

Chloride: white
Bromide: cream
Iodide: yellow

Question 20

How do you test for sulfates and what precipitates do they form?

Answer 20

Add dilute hydrochloride acid and barium chloride. They form a white precipitate.

Question 21

Required practical 7: identifying compounds.
Equipment:

Answer 21

Nichrome wire, lime water, hydrochloride acid.

Question 22

Required practical 7: identifying ions.
Method:

Answer 22

• pour 1cm cubed of each known chloride solution into 5 test tubes.
• clean the nichrome wire by dipping it into the dilute hydrochloric acid.
• dip the nichrome wire into solution and the hold the tip in a blue Bunsen flame.
• repeat the following solution and make sure to clean the wire after each test.
• record the colour of the flame and compare results with the matching colour flame.

Question 23

What is an instrumental method used for?

Answer 23

Can be used to identify compounds and elements.

Question 24

What is an advantage of an instrumental method?

Answer 24

They are sensitive, accurate and rapid.

Question 25

What is flame emission spectroscopy used for?

Answer 25

To analyse metal ions in solutions.

Question 26

How does flame emission spectroscopy work?

Answer 26

• Sample is put into a flame and the light given out is passed through a spectroscope.
• output is a line spectrum that can be analysed to identify metal ions in the solution and measure their concentrations.