JEE Main 2022 · 26 June · evening · Single correct · +4 / −1
The role of depressants in 'Froth Flotation method' is to
- (a) selectively prevent one component of the ore from coming to the froth.
- (b) reduce the consumption of oil for froth formation.
- (c) stabilize the froth.
- (d) enhance non-wettability of the mineral particles.
Answer and solution
Answer (a) selectively prevent one component of the ore from coming to the froth.
Solution
Chemistry ma’am · 3 steps
A depressant does not help the froth at all; it holds one sulphide back so the other floats alone.
- Four kinds of helpers. Froth flotation uses water, oil and air, plus a few added chemicals. Each added chemical has one specific job, so match the job to the name.
Reagent Example Its job Collector pine oil, fatty acids, xanthates makes mineral particles non-wettable by water, so they stick to the froth Froth stabiliser cresols, aniline keeps the froth from collapsing Depressant NaCN stops one chosen mineral from reaching the froth - How it works. In an ore holding both PbS and ZnS, NaCN forms a complex, Na₂[Zn(CN)₄], on the ZnS surface. That keeps ZnS out of the froth, while PbS still floats and is separated.
- So. A depressant selectively prevents one component of the ore from coming to the froth, which is option (a).
The idea to keep. In froth flotation, collectors make particles float, stabilisers keep the froth alive, and depressants hold back one mineral so two sulphides can be separated.
Answer from the NTA final answer key. Solution by PrepWiser.