JEE Main 2021 · 26 August · evening · Single correct · +4 / −1
Given below are two statements :
Statement I : Sphalerite is a sulphide or of zinc and copper glance is a sulphide ore of copper.
Statement II : It is possible to separate two sulphide ores by adjusting proportion of oil to water or by using 'depressants' in a forth flotation method.
Choose the most appropriate answer from the options given below :
- (a) Statement I is true but Statement II is false.
- (b) Both Statement I and Statement II are true.
- (c) Statement I is false but Statement II is true.
- (d) Both Statement I and Statement II are false.
Answer and solution
Answer (b) Both Statement I and Statement II are true.
Solution
Chemistry ma’am · 4 steps
Check each statement on its own: name the ore's formula, then ask how froth flotation can be tuned.
- Statement I. Sphalerite (zinc blende) is ZnS, a sulphide ore of zinc. Copper glance (chalcocite) is Cu₂S, a sulphide ore of copper. So Statement I is true.
- How flotation works. In froth flotation, sulphide particles are wetted by the oil and rise with the froth. The gangue is wetted by the water and sinks.
- Statement II. Two sulphides do not respond to oil equally. So changing the oil-to-water ratio, or adding a depressant, lets one ore float while the other stays back. For example, NaCN forms a complex on the surface of ZnS and keeps it out of the froth, so PbS floats alone. Statement II is true.
- So. Both statements are correct, which is option (b).
The idea to keep. Froth flotation is for sulphide ores, and it can even split two sulphides. Tune the oil-to-water ratio or add a depressant like NaCN to hold one back.
Answer from the NTA final answer key. Solution by PrepWiser.