Chemical analysis

Question 1

What are the properties and test for hydrogen?

Answer 1

• colourless, combines violently with oxygen when ignited

The test for hydrogen uses a burning splint held at the open end of a test tube of the gas. Hydrogen burns rapidly with a pop sound.

Question 2

What are the properties and test for oxygen?

Answer 2

• colourless, helps fuels burn more readily than in ai

The test for oxygen uses a glowing splint inserted into a test tube of the gas. The splint relights in oxygen

Question 3

What are the properties and test for Co2?

Answer 3

• colourless
• The test for carbon dioxide uses an aqueous solution of calcium hydroxide (lime water). When carbon dioxide is shaken with bubbled through limewater the limewater turns milky (cloudy).
• connect test tube with a test tube of limewater

Question 4

What is the test for Chlorine?

Answer 4

The test for chlorine uses litmus paper. When damp litmus paper is put into chlorine gas the litmus paper is bleached and turns white.

Question 5

What are the different ways you can identify metal ions (cations)

Answer 5

• flame tests
• sodium hydroxide solution

Question 6

What are the colours produced in a flame test for :

• lithium
• sodium
• potassium
• calcium
  -copper

Answer 6

• lithium compounds result in a crimson flame
• sodium compounds result in a yellow flame
• potassium compounds result in a lilac flame
• calcium compounds result in an orange-red flame
• copper compounds result in a green flame.

Question 7

Name the colour of precipitate produced for each of these metals when they are added to sodium hydroxide solution:

• aluminium
• calcium
• magnesium
• copper (III)
• iron (II)
• iron (III)

Answer 7

Solutions of aluminium, calcium and magnesium ions form white precipitates

only the aluminium hydroxide precipitate dissolves in excess sodium hydroxide solution

Copper(II) forms a blue precipitate,

iron(II) a green precipitate
iron(III) a brown precipitate.

Question 8

How to test for carbonates?

Answer 8

Carbonates react with dilute acids to form carbon dioxide gas ( +salt and water)

Carbon dioxide can be identified with limewater.

Question 9

What are carbonates and its properties?

Answer 9

carbonates are substances that contains CO3 (2-) ions

most are insoluble

sodium carbonate and potassium carbonate are soluble and dissolvable in water to form solutions that contain carbonate ions

Question 10

How to test for Halides?

Answer 10

Halide ions in solution produce precipitates with silver nitrate solution in the presence of dilute nitric acid.

Add a couple of drops of dilute nitric acid, followed by a couple of drops of silver nitrate solution to your unknown solution

Question 11

What colour precipitate do silver chloride, silver bromide and silver iodide form?

Answer 11

Silver chloride is white,
silver bromide is cream
silver iodide is yellow.

Question 12

How do you test for sulfates

Answer 12

Sulfate ions in solution produce a white precipitate with barium chloride solution in the presence of dilute hydrochloric acid.

use a pipette to add a couple of drops of dilute hydrochloric acid followed by a couple of drops of barium chloride solution to a test tube containing an unknown solution

Question 13

How do you test for the presence of water?
What is the equation?
What happen when water is added in excess?

Answer 13

identified using solid copper(II) sulfate, CuSO4(s).

This solid is white when anhydrous but blue when hydrated.

CuSO4(s) + 5H2O(l) → CuSO4·5H2O(s)

If excess water is added, the copper(II) sulfate will dissolve to form a blue solution, CuSO4(aq).

Question 14

What is the test for ammonia

Answer 14

Damp red litmus paper which turns blue