Tag: concentration of ore

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

An ore on heating in air forms $SO _{2}$. State the process that will be used for its concentration.

  1. Hydrautic washing

  2. Magnetic separation

  3. Froth floatation

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Whenever a metal sulphide is heated in air, sulphur dioxide is formed as one of the products. A sulphide ore is concentrated by the froth floatation process.

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

In froth floatation process, gangue particles are wetted by pine oil.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Froth flotation is a process to purify sulfide ores, in presence of pine oil. The oil acts as hydrophobic agent and forms froth with hydrophobic impurities (gangue) which is skimmed off from the surface leaving behind the concentrated mineral.
Wet pine oil is used in froth flotation process because it does not have an affinity towards water (because of the hydrophobic chemicals as its constituents)and it attracts impurities which can be washed away.
Hence, it is true.
Multiple choice chemistry principles of metallurgy concentration of ore concentration of ores general principles of metallurgy

Identify the principle behind the concentration of bauxite ore:

  1. magnetic property of impurities in white bauxite
  2. low specific gravity of $Al _2O _3$
  3. amphoteric nature of $Al _2O _3$
  4. high melting point of $Al _2O _3$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

An amphoteric compound is a compound that can react both as an acid as well as a base. For example, $ Al _{ 2 }{ O } _{ 3 } $. 

Hence, this principle is behind the concentration of bauxite ore. In this process $ Al _{ 2 }{ O } _{ 3 } $ first acts as an acid then as a base.

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

The method used for the concentration of sulphide ores is:

  1. froth floatation

  2. smelting

  3. magnetic separatio

  4. gravity separation
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Froth flotation is a process for selectively separating hydrophobic materials from hydrophilic. The principle of froth flotation process is that sulphide ores are preferentially wetted by the pine oil, whereas the gangue particles are wetted by the water. Hence the method used for the concentration of sulphide ores is froth flotation.

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

Extraction of gold $\left( Au \right) $ involves the formation of complex ions '$X$' and '$Y$'.
        Gold ore $\underset { C{ N }^{ - },{ H } _{ 2 }O,{ O } _{ 2 } }{ \underrightarrow { \quad Roasting\quad  }  } \quad H{ O }^{ - }+'X'\quad \underrightarrow { \quad \quad \quad Zn\quad \quad \quad  } \quad 'Y'+Au$
'$X$' and '$Y$' are respectively

  1. $Au{ \left( CN \right) } _{ 2 }^{ - }$ and $Zn{ \left( CN \right) } _{ 4 }^{ 2- }$
  2. $Au{ \left( CN \right) } _{ 4 }^{ 3- }$ and $Zn{ \left( CN \right) } _{ 4 }^{ 2- }$
  3. $Au{ \left( CN \right) } _{ 3 }^{ - }$ and $Zn{ \left( CN \right) } _{ 6 }^{ 4- }$
  4. $Au{ \left( CN \right) } _{ 4 }^{ - }$ and $Zn{ \left( CN \right) } _{ 3 }^{ - }$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Extraction of gold $(Au)$ involves the formation of complex ions $'X'$ and $ 'Y'. 'X'$ and $'Y'$ are $\displaystyle Au{ \left( CN \right)  } _{ 2 }^{ - }$ and $\displaystyle Zn{ \left( CN \right)  } _{ 4 }^{ 2- }$ respectively

 Gold ore $\displaystyle \underset { C{ N }^{ - },{ H } _{ 2 }O,{ O } _{ 2 } }{ \underrightarrow { \quad Roasting\quad  }  } \quad H{ O }^{ - }+\underset {'X'}{Au{ \left( CN \right)  } _{ 2 }^{ - }} \quad \underrightarrow { \quad \quad \quad Zn\quad \quad \quad  } \quad \underset {'Y'}{Zn{ \left( CN \right)  } _{ 4 }^{ 2- }}+Au \downarrow$

Note:
The complex X is water soluble.
More electropositive zinc displaces gold from complex.

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

During leaching, gold is recovered from the solution by the addition of ______.

  1. zinc

  2. zinc oxide

  3. silver oxide

  4. zinc sulphide
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Gold is recovered from the solution by the addition of zinc.
$  2[Au(CN) _2]^- + Zn\rightarrow  [Zn(CN) _4]^{2+} +2 Au$
Note:
Gold ore is concentrated by leaching with sodium cyanide in presence of air.
$4Au +8CN^-+2H _2O +O _2 \rightarrow 4[Au(CN) _2]^-+4OH^-$