Older MCQs might not have the typical A, B, C,
D
choices. They
have choices 1, 2, 3, and a combination of them is the answer. Below is the key that maps such
combinations to the answer.
A
1, 2 and 3 are correct
B
1 and 2 only are correct
C
2 and 3 only are correct
D
1 only is correct
State that some of these substances are potentially harmful, including: (a) some metal compounds are toxic (b) some plastics harm aquatic life (c) sewage contains harmful microbes which cause disease (d) nitrates and phosphates lead to deoxygenation of water and damage to aquatic life Details of the eutrophication process are not required
Describe tests to identify the anions: (a) carbonate, CO3^2-, by reaction with dilute acid and then testing for carbon dioxide gas (b) chloride, Cl^-, bromide, Br^-, and iodide, I^-, by acidifying with dilute nitric acid then adding aqueous silver nitrate (c) nitrate, NO3^-, by reduction with aluminium foil and aqueous sodium hydroxide and then testing for ammonia gas (d) sulfate, SO4^2-, by acidifying with dilute nitric acid then adding aqueous barium nitrate (e) sulfite, SO3^2-, by reaction with acidified aqueous potassium manganate(VII)
