chpt 7 acids and bases

Question 1

Define basic oxides.

Answer 1

1. MOST metallic oxides are basic with the exception of the amphoteric oxides
2. most are soluble in water
3. react only with acids to form salt and water

Question 2

Define amphoteric oxides.

Answer 2

1. zinc aluminium and lead
2. soluble in water
3. reacts with both acids and bases to from salt and water

Question 3

What are the colours of the universal indicator and what do they represent ?

Answer 3

1. red (most acidic)
2. yellow / orange (weak acid)
3. green (neutral)
4. blue (weak alkali)
5. violet / purple (strong alkali)

Question 4

Importance of soil and ph and how to treat them ?

Answer 4

1. Most plants grow best in slightly acidic / neutral situations ph 6-7
2. acidic soil is a problem caused by acid rain and acidic fertilisers
3. calcium oxide (quicklime) / slaked lime (calcium hydroxide) used to balance out ph
4. do not add quicklime / slaked lime with a ammonium based fertiliser as it will form ammonia gas
5. plants no longer to absorb the ammonium ion which provides it with the nitrogen that it needs
6. quicklime / slaked lime used to neutralise soil’s acidity is also lost