6 Markers

Question 1

Describe a test that you would carry out on an unknown solid to see if it contains bromine. (Exam might give you a random chemical like ammonium bromide) List bullet-points/stages that you would highlight in your answer.

Answer 1

To test for bromide ions:

1. Add silver nitrate
2. If a creamy-white precipitation is given off bromine ions are present.

Question 2

Describe a test to identify ammonium on an unknown solid.

Answer 2

• add sodium hydroxide
• this makes ammonia gas (distinct)
• solution may need warming
• moist red litmus paper can detect ammonia gas.

Question 3

Explain methods in treating the hardness of hard water.

Answer 3

• for temporary hardness - boil the water - hydrocarbonate decomposes into calcium carbonate (visible limescale).
• for permanent hardness - contains many different dissolved calcium compounds - ions exchange resin is needed to swap the calcium ions with sodium ions to make the water soft.

Question 4

Electrolysis 6 marker may come up. List some facts about electrolysis.

Answer 4

• has two electrodes - a cathode and an anode.
• negative ions (anions) attract to positive anode, and cations to cathode.
• copper usually forms at cathode, and other element at anode which you can describe the test for.