All Prescribed Practicals

Question 1

Give the colour changes for methyl orange and phenolphalein

Answer 1

1. phenolphthalein :

• colourless in acid.
• pink in alkali solutions.
• colourless in neutral solutions

2. methyl orange :

• red in acid.
• yellow in alkali solutions.
• orange in neutral solutions

Question 2

What colour precipitate does a Cu²⁺ ion cause when dissolved in sodium hydroxide/ammonia solution?

Answer 2

• Blue ppt in excess sodium hydroxide
• Deep blue ppt in excess ammonia solution

Question 3

What colour precipitate does a Fe²⁺ ion cause when dissolved in sodium hydroxide/ammonia solution?

Answer 3

Green ppt

Question 4

What colour precipitate does a Fe³⁺ ion cause when dissolved in sodium hydroxide/ammonia solution?

Answer 4

Red-brown ppt

Question 5

What colour precipitate does a Mg²⁺ ion cause when dissolved in sodium hydroxide/ammonia solution?

Answer 5

White ppt

Question 6

What colour precipitate does a Al³⁺ ion cause when dissolved in sodium hydroxide/ammonia solution?

Answer 6

White ppt in excess sodium hydroxide

But

Dissolves in excess ammonia solution

Question 7

What colour precipitate does a Zn²⁺ ion cause when dissolved in sodium hydroxide/ammonia solution?

Answer 7

White ppt

Which dissolves in both solutions

Question 8

What colour precipitate does a Cl^- ion cause when dissolved in silver nitrate solution?

Answer 8

White ppt

Question 9

What colour precipitate does a Br^- ion cause when dissolved in silver nitrate solution?

Answer 9

Cream ppt

Question 10

What colour precipitate does a I^- ion cause when dissolved in silver nitrate solution?

Answer 10

Yellow ppt

Question 11

What colour precipitate does a SO₄^- ion cause when dissolved in barium chloride solution?

Answer 11

White ppt

Question 12

What is the test for a CO₃^- ion?

Answer 12

Add dilute acid to the solid and test gas with limewater

Bubbles, limewater turns milky from colourless

Question 13

C3

Describe how a pure, dry sample of hydrated calcium chloride may be prepared from solid calcium carbonate and hydrochloric acid. (6)

Answer 13

• place hydrochloric acid in a beaker/conical flask
• add calcium carbonate until in excess/no more gas given off
• filter
• heat filtrate to half volume
• allow to cool and crystallise
• filter off crystals
• dry between two sheets of filter paper/in a desiccator/in a low temperature oven

Question 14

Why are rough titrations used?

Answer 14

To estimate the end point / allow faster subsequent titrations

Question 15

State the colour change observed in the solution when copper(II) carbonate is added to propanoic acid

Answer 15

Colourless to blue

Question 16

What pH readings denote a:

• strong alkali
• weak alkali
• neutral
• weak acid
• strong acid

Answer 16

• S Al - 12-14
• W Al - 8-11
• N - 7
• W Ac - 3-6
• S Ac - 0-2

Question 17

What apparatus are used to react steam with a metal (9)

Answer 17

• a boiling tube
• damp mineral wool
• the metal (in front of the wool)
• a heat source
• a delivery tube & a bung
• a trough
• filled with water
• a beehive shelf
• a gas chamber

Question 18

What is heating to constant mass? (2)

Answer 18

• When salts containing water of crystallisation are heated and weighed
• until their mass doesn’t change

Question 19

C5

How do you investigate the reactivity of metals (5)

How do you ensure its a fair test?

Answer 19

• use a salt solution
• for displacement reactions
• measure temperatures before and after
• repeat and get an average temperature change
• the metal which has the greatest average temperature rise = most reactive

2. • Ensure the surface area / volume of metals is the same
   • Ensure the volume of the salt solution is the same
     Etc.