Tag: general principles of metallurgy

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Questions Related to general principles of metallurgy

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.
$4Au +8CN^-+2H _2O +O _2 \rightarrow 4[Au(CN) _2]^-+4OH^-$

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

Which of the following ore is best concentrated by froth flotation method ?

  1. Galena

  2. Cassiterite

  3. Magnetite

  4. Zinc blende
Reveal answer Fill a bubble to check yourself
A,D Correct answer
Explanation

Galena ($PbS$) and zinc blende ($ZnS$) are sulphide ores. Cassiterite $SnO _{2}$ (oxide ore), and Magnetite $Fe _{3}O _{4}$ (oxide ore) are not sulphide ore. The froth flotation process is used to concentrate sulphide ores, based on preferential wetting properties with frosting agent and water.

Hence option $A$ and $D$ are correct.

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

Minerals from which metals can be preferably extracted are called :

  1. Ores

  2. Source

  3. Alloy

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$\Rightarrow$ Minerals occur naturally in the Earth.

$\Rightarrow$ The minerals from which the metals are extracted without loss is called ores.
Example:
Many minerals are there for Aluminium extraction. But Bauxite extraction is of low cost. So Bauxite is only called ore of Aluminium. But remaining are only minerals.

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

In the process of extraction of gold,
1.) Roasted Au ore $+ \ CN^- _{(aq)} + O _2 \longrightarrow [X] + NaOH$

2.) $[X] + Zn \longrightarrow [Y] + Au$

  1. $X = [Au(CN) _2]^-, Y = [Zn(CN) _4]^{2-}$
  2. $X = [Au(CN) _4]^{2-}, Y = [Zn(CN) _4]^{2-}$
  3. $X = [Au(CN) _2]^-, Y = [Zn(CN) _6]^{4-}$
  4. $X = [Au(CN) _4]^-, Y = [Zn(CN) _4]^{2-}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
This reaction is an example of the Cyanide process (Mac Arthur Forrest Process) for extraction of metals like gold or silver.

Reaction:

$Au + 8NaCN +2H _2O + O _2 \rightarrow 4Na[Au(CN) _2 ] + 4NaOH$

Gold is obtained by reaction with Zn:

$2Na[Au(CN) _2] + Zn \rightarrow  Na _2[Zn(CN) _4 ] +  2Au$


Therefore, $X = [Au(CN) _2]^-$ and $Y = [Zn(CN) _4]^{2-}$

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

Froth floatation process used for the concentration of sulphide ore:

  1. is based on the difference in wettability of different minerals
  2. uses sodium ethyl xanthate ($C _2H _5OCS _2Na$) as a collector
  3. uses $NaCN$ as depressant in the mixture of $ZnS$ and $PbS$ when $ZnS$ forms soluble complex and $PbS$ forms froth

  4. uses pine oil as frothing agent
Reveal answer Fill a bubble to check yourself
A,B,C,D Correct answer
Explanation

Froth flotation is a process for selectively separating hydrophobic materials from hydrophobic. In some cases, for example, sulphides ores of copper, zinc and lead concentration is brought by this method. In this method, the advantage is taken of the preferential wetting of the ore by an oil.The finely ground ore is taken in a tank containing water and 1% of pine oil or turpentine oil.
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. By this flotation method, it is possible to concentrate over 90% of a sulphite ore to 1/10 of its original bulk.
During the flotation process of some ores, these substances are added which activate or depress the flotation property of the minerals and thus help in the separation of minerals present in the ore. For instance, galena (PbS) is usually associated with sphalerite (ZnS) and pyrites ,NaCN.
Hence all options are correct.