Tag: concentration of ores

Questions Related to concentration of ores

Forth floatation process of concentration is based on the:

chemistry principles of metallurgy concentration of ore concentration of ores general principles of metallurgy

  1. preferential wetting properties with the frothing agent and water

  2. difference in the specific gravities of gangue and ore particles

  3. difference in solubility of ganaue and ore particles in frothing agent and water

  4. difference in reactivity of gangue and ore particles with water and frothing agent.

Show answer
Correct Option: A
Explanation:
  • Froth floatation process method is used for removing gangue from sulphide ores.
  •  In this process, a suspension of the powdered ore is made with water. Collectors and froth stabilizers are added to it. 
  • Collectors (e.g., pine oils, fatty acids, xanthates, etc.) enhance non-wettability of the mineral particles and froth stabilizers (e.g., cresols, aniline) stabilize the froth.
  • The mineral particles become wet by oils while the gangue particles by water. 

For which of the following ores forth floatation method is used for concentration?

chemistry principles of metallurgy concentration of ore concentration of ores general principles of metallurgy

  1. Haematite

  2. Zinc blende

  3. Magnetite

  4. Carnallite

Show answer
Correct Option: B
Explanation:
  • Froth floatation method is used for removing gangue from sulphide ores. In this process, a suspension of the powdered ore is made with water
  • Among the given options Zinc blend ($ZnS$) is the only sulphide ore and hence Froth floatation process is used for its concentration.
  • Hence, option B is the right answer.

Which of the following metals is not extracted by leaching?

chemistry principles of metallurgy concentration of ore concentration of ores general principles of metallurgy

  1. Aluminium

  2. Mercury

  3. Silver

  4. Gold

Show answer
Correct Option: B
Explanation:

Leaching is a process where ore is soluble and impurities are insoluble, widely used extractive metallurgy technique which converts metals into soluble salts in aqueous media.
Bauxite, SIlver and gold ores are usually soluble in some solvents and hence leaching is used to concentrate them.
Hence, option $B$ is the correct answer.

Which of the following statements is correct about the role of collectors added during forth floatation process?

chemistry principles of metallurgy concentration of ore concentration of ores general principles of metallurgy

  1. Collectors enhance the non-wettability of ore particles

  2. Collectors enhance the wettability of gangue particles

  3. Collectors help in separating two sulphide ores present in the mixture

  4. Collectors help ore particles to settle down below the froth

Show answer
Correct Option: A
Explanation:
  • Froth floatation method is used for removing gangue from sulphide ores. In this process, a suspension of the powdered ore is made with water.
  • Collectors and froth stabilizers are added to it. Collectors (e.g., pine oils, fatty acids, xanthates, etc.) enhance non-wettability of the mineral particles and froth stabilizers (e.g., cresols, aniline) stabilize the froth.
  • The mineral particles become wet by oils while the gangue particles by water.

Which of the following ores is concentrated by chemical leaching method?

chemistry principles of metallurgy concentration of ore concentration of ores general principles of metallurgy

  1. Cinnabar

  2. Argentite

  3. Copper pyrites

  4. Galena

Show answer
Correct Option: B
Explanation:
  • In the metallurgy of silver , the respective metal is eached with a dilute solution of NaCN or KCN in the presence of air, which supplies $O _2$. The metal is obtained later by replacement reaction.
  • The reactions involved are-
$4Ag+8CN^{-}+2H _2O+O _2 \rightarrow 4[M(CN) _2]^{-}+4OH^{-}$

$2[Ag(CN) _2]^{-}+Zn \rightarrow [Zn(CN) _4]^{2-}+2Ag$
  • Hence, Argentite being an ore of SIlver is concenrated by leaching.

Which type of ores are concentrated by froth flotation process?

chemistry general principles of metallurgy concentration of ore concentration of ores principles of metallurgy

  1. Carbonates

  2. Sulphides

  3. Oxides

  4. Phosphates

Show answer
Correct Option: B
Explanation:

The froth flotation method is used to separate and concentrate ores by altering their surfaces to a hydrophobic or hydrophilic condition.


This method is based on the principle of the difference in the wetting properties of the ore and the gangue particles with the water and oil.


Therefore, sulphide ores preferably wetted by the oil and the gangue with the water.
Hence, option $(B)$ is correct.

When $ZnS$ and $PbS$ minerals are present together, then $NaCN$ is added to separate them in the froth flotation process as a depressant, because:

chemistry general principles of metallurgy concentration of ore concentration of ores principles of metallurgy

  1. $Pb(CN) _2$ precipitated while no effect on $ZnS$

  2. $ZnS$ forms soluble complex $Na _2 Zn(CN) _4$

  3. $PbS$ forms soluble complex $Na _2Pb(CN) _4$

  4. both $(a)$ and $(b)$

Show answer
Correct Option: B
Explanation:

$NaCN$ prevents $ZnS$ from forming the froth by reacting with it to from complex $Na _2[Zn(CN) _4]$ and acts as a depressant. While it does not prevent $PbS$ from forming froth and both the ores can easily be separated.

Froth floatation process is used for the :

chemistry principles of metallurgy concentration of ore concentration of ores general principles of metallurgy

  1. Oxide ores

  2. Sulphide ores

  3. Chloride ores

  4. All of these

Show answer
Correct Option: B
Explanation:

Froth floatation process is used for the sulphide ores. In this method, wetting of the ore by an oil takes place. A strong current of air is blown through the suspension, producing a heavy froth or foam on the surface. The metal sulphide is wetted by the oil but the gangues is not and the sulphide-oil mixture is carried to the surface by films of oil The froth is skimmed off, the gangue settles down on the bottom or remains underneath the froth.

Which of the following fraction of coal tar distillation is obtained at $270^{\circ} - 360^{\circ} C$?

chemistry principles of metallurgy concentration of ore concentration of ores general principles of metallurgy

  1. Light oil

  2. Middle oil

  3. Green oil

  4. Heavy oil

Show answer
Correct Option: C
Explanation:

Green oil (anthracene oil) is obtained at $270 - 360^{\circ} C$ by distillation of coal tar. It mainly has anthracene and phenanthrene.

Concentration by froth floatation is applicable for which of the following ores?

chemistry principles of metallurgy concentration of ore concentration of ores general principles of metallurgy

  1. $Al _{2}O _{3}$

  2. $Te _{3}O _{4}$

  3. $Te _{2}O _{3}.3H _{2}O$

  4. $ZnS$

Show answer
Correct Option: D
Explanation:

This method is used for those metals whose ore gets preferably wetted by the oil and the gangue by the water. The sulphide ores preferably wetted by the oil and the gangue with the water.