Tag: principles of metallurgy

Questions Related to principles of metallurgy

Bauxite is concentrated by:

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

  1. Chemical method

  2. Roasting

  3. Magnetic separation

  4. Froth flotation process

Show answer
Correct Option: A
Explanation:

The bauxite is purified by the Bayer Process. First the ore is mixed with a hot concentrated solution of sodium hydroxide. The $NaOH$ will dissolve the oxides of aluminum and silicon but not other impurities such as iron oxides, which remains insoluble. The insoluble materials are removed by filtration.This method is called the chemical method.

In the froth floatation process, for the beneficiation of ores, the ore particles float because ______________.

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

  1. they are light

  2. their surface is not easily wetted by water

  3. they bear electrostatic charge

  4. they are insoluble

Show answer
Correct Option: B
Explanation:

In the froth floatation process, for the benefaction of ores, the ore particles float because their surface is not easily wetted by water. This method is base on the difference in the wetting properties of ores and gangue particles with the water and oil.

Which of the following process is not a physical process of separation?

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

  1. Levigation

  2. Magnetic separation

  3. Leaching

  4. Froth fioatation

Show answer
Correct Option: C
Explanation:

Leaching involves the treatment of the ore with a suitable reagent to make it soluble while impurity remains insoluble. The ore is recovered from the solution by suitable chemical method.

For example Bayer's process:
Bauxite ore contains impurities like $Fe _2O _3$, $TiO _2$  and $SiO _2$. So, when it dissolve in aq. NaOH/pressure + 150°C T, bauxite dissolves but others donot dissolve. 
$Al _2O _3 + 2NaOH \rightarrow 2NaAlO _2 + H _2O$
$ NaAlO _2 + 2H _2O \rightarrow Al(OH) _3 + NaOH$

Which one of the following is not a method of concentration of metals?

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

  1. Gravity separation

  2. Froth flotation process

  3. Electromagnetic separation

  4. Smelting

Show answer
Correct Option: D
Explanation:
Smelting is not a method of concentration of metals.

Smelting is a process of extraction of metal in its molten state by any reducing agent in the presence of flux. 

For example: oxides of less electropositive metals like Pb, Zn, Fe, Cu are reduced by any other reducing agents.

Chemical leaching is not useful in the concentration of:

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

  1. copper pyrite

  2. bauxite

  3. galena

  4. cassiterite

Show answer
Correct Option: A,C,D
Explanation:
Chemical leaching is a process widely used in extractive metallurgy where ore is treated with chemicals to convert the valuable metals within into soluble salts while impurity remains insoluble.

Examples : copper pyrites, galena and cassiterite.

Hence options A,C & D are correct.

Froth floatation process is used to concentrate magnetic ores.

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

  1. True

  2. False

Show answer
Correct Option: B
Explanation:

Froth floatation process is used to concentrate sulphide ores. In some cases, sulphide ores of copper, zinc and lead concentration are brought by this method. It is the referential wetting of the ore by an oil. A strong current of air is blown through the suspension producing a heavy froth e.g. Galena $(PbS)$ is associated with Sphalerite $(ZnS)$ and Pyrite $(FeS)$.

 Name the metal which are associated with the following term in their extraction from their ores. Magnetic separation:

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

  1. tin stone and chromite ore

  2. copper stone and chromite ore

  3. tin stone and iron ore

  4. none of these

Show answer
Correct Option: C
Explanation:
 This method is adopted when either ore or the impurities are magnetic in nature. They are separated from each other by means of magnetic separators. Eg: $SnO _2$ (Non magnetic) in $Fe _3O _4$ (magnetic)

Sulphide ore of copper can be concentrated by froth floatation process.

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

  1. True

  2. False

Show answer
Correct Option: A
Explanation:
Froth Floatation Process:- The process is best suitable for sulphide ores. The process is based on different wetting characteristics of the ore and gangue particles with water and pine oil. The ore is wetted by oil and impurities are wetted by water. Ore particles are adsorbed on potassium or sodium ethyl xanthate (as collector) and come at the surface along with the froth. Froth stabilisers (cresols, aniline) stabilise the froth. So sulphide of copper can be concentrated by froth floatation process.

Sulfide ores are usually dressed by the _____ process.

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

  1. sieve process

  2. froth floatation

  3. magnetic floatation

  4. none of these

Show answer
Correct Option: B
Explanation:

Froth floatation process is based on the principle that the metallic sulphide particles of ore are preferentially wetted by oil and the gangue particles by water.
Sulphide ores being lighter are easily wetted by oil to come on the surface of solution with froths during froth floatation process, leaving behind heavy matter of gangue wetted by water.
Sulphide ores are usually dressed by froth floatation process.

The oil used in the froth floatation method for the purification of ore is _________.

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

  1. Coconut oil

  2. Olive oil

  3. Pine oil

  4. Castor oil

Show answer
Correct Option: C
Explanation:
Froth Floatation process is suitable for sulphide ores. The process is based on different wetting characteristics of the ore and gangue particles with water and pine oil. 

The ore is wetted by oil and impurities are wetted by water. Ore particles are adsorbed on potassium or sodium ethyl xanthate (as a collector) and come at the surface along with the froth. Froth stabiliser (cresols, aniline) stabilise the froth. 

So, the correct option is $C$