C3.4 Analysing substances

Question 1

How can you measure the volumes of acid and alkali solutions that react with each other?

Answer 1

A titration using a suitable indicator

Question 2

What are the compounds and colours for the 5 flame tests? (Crazy Yaks Love Responsible Giraffes)

Answer 2

• Lithium= Crimson
• Sodium= Yellow
• Potassium= Lilac
• Calcium= Red
• Barium= Green

Question 3

Which ions form white precipitates with sodium hydroxide solution? (NaOH CAM)

Answer 3

• Calcium
• Aluminium
• Magnesium

Question 4

What happens to an aluminium hydroxide precipitate with excess sodium hydroxide solution?

Answer 4

It dissolves

Question 5

Which ions form coloured precipitates with sodium hydroxide solution, and what are their colours?

Answer 5

• Copper (II) Blue
• Iron (II) Green
• Iron (III) Brown

Question 6

Which ions in solution produce precipitates with silver nitrate solution in the presence of dilute nitric acid?
(Name 3)

Answer 6

Halide ions:

• Silver chloride
• Silver bromide
• Silver iodide

Question 7

What colour precipitates do the halide ions produce?

Answer 7

• Silver chloride= white
• Silver bromide= cream
• Silver iodide= yellow

Question 8

Which ions form a white precipitate with barium chloride solution in the presence of dilute hydrochloric acid?

Answer 8

Sulfate ions

Question 9

What is the process of a titration? Expand on these points:

1) Acid 2)Pipette 3)Indicator 4)Burette 5)Tile
6) Colour change 7)Record

Answer 9

1) Acid in conical flask
2) Volume of acid measured using pipette
3) Indicator in flask
4) Alkali in burette
5) Flask on tile
6) Swirl and note for colour change
7) Record alkali volume added

Question 10

What can you use the results of a titration for if the concentration of one of the reactants is known?

Answer 10

The concentration of the other reactant