(i) Collectors enhance the non-wettability of the mineral particles.

(ii) Collectors enhance the wettability of gangue particles.

(iii) By using depressants in the process two sulphide ores can be separated.

(iv) Froth stabilisers decrease wettability of gangue.

Correct Answers:

(i) Collectors enhance the non-wettability of the mineral particles.

(iii) By using depressants in the process two sulphide ores can be separated.

Explanation: The role of substances added in the froth floatation process is that the collectors enhance the non-wettability of the mineral particles and by using depressants in the process two sulphide ores can be separated.