Tag: concentration of ores

Questions Related to concentration of ores

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

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

  1. Galena

  2. Cassiterite

  3. Magnetite

  4. Zinc blende

Show answer
Correct Option: A,D
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.

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

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

  1. True

  2. False

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Correct Option: A
Explanation:

Froth flotation is selective separating the hydrophilic particles from hydrophobic. It is used for copper and lead sulfide ores. It is the preferential wetting of ore with pine oil to remove gangue or impurities.

Minerals from which metals can be preferably extracted are called :

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

  1. Ores

  2. Source

  3. Alloy

  4. None of these

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Correct Option: A
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.

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

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

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

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

Show answer
Correct Option: A
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 $Y = [Zn(CN) _4]^{2-}$

Froth floatation process used for the concentration of sulphide ore:

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

  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

Show answer
Correct Option: A,B,C,D
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.

In the equation,


$4M + 8 CN^- + 2 H _2O + O _2 \longrightarrow 4[M(CN) _2]^- + 4 OH^-$

the metal M is:

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

  1. Copper

  2. Silver

  3. Gold

  4. Zinc

Show answer
Correct Option: B,C
Explanation:

Cyanide process, also called Macarthur-Forrest Process, method of extracting silver and gold from their ores by dissolving them in a dilute solution of sodium cyanide or potassium cyanide. 


The process was invented in 1887 by the Scottish chemists John S. MacArthur, Robert W. Forrest, and William Forrest.

$4Ag + 8 CN^- + 2 H _2O + O _2 \longrightarrow 4[Ag(CN) _2]^- + 4 OH^-$


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


Hence options B & C are correct.

Select the correct statement(s) :

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

  1. Gravity separation method is used in concentration of oxide ore and carbonate ore

  2. Magnetic separation method is used for separation of non-magnetic rutile and magnetic impurity of chlorapatite

  3. $Fe _3O _4$ is magnetic and impurities non-magnetic

  4. $MnO _2$ is non-magnetic and impurities magnetic

Show answer
Correct Option: A,C
Explanation:
A) Gravity separation is an industrial method of separating two components, either a suspension, or dry granular mixture where separating the components with gravity is sufficiently practical: i.e. the components of the mixture have different specific weight. All of the gravitational methods are common in the sense that they all use gravity as the dominant force. The working principle is to lift the material by vacuum over an inclined vibrating screen covered deck.So by gravity separation we remove impurities present in oxides and carbonates there by oxides and carbonates are concentrated.

B) Magnetic separation is a process in which magnetically susceptible material is extracted from a mixture using a magnetic force. But non magnetic substances are not separated.

C) $Fe _3O _4$, is magnetic and impurities non-magnetic.

D) $MnO _2$, is magnetic substance.

Hence options A  &C are correct.

All minerals are not the ore but all ores are minerals. The extraction of a particular metal depends upon several factors and overall it has to be convenient and economical.


Which of the following statement is true?

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

  1. Na-ethyl xanthate is used as frother exclusively.

  2. Levigation cannot be applied for sulphide in any condition.

  3. Froth floatation can be applied for non-sulphide ore also using suitable activator.

  4. Impurities like S and As are removed as elemental vapor in roasting.

Show answer
Correct Option: C
Explanation:

(A) Sodium ethylxanthate acts as collector and not frother.


(b) Levigation can be used for sulphide ore to remove majority of gangue when density difference is high.

(C) Froth floatation can be used for non-sulphide ores having sulphide impurities, and the ore is recovered by using suitable activator.

(D) During roasting, impurities such as S and As are removed as their volatile oxides $SO _2$ and $As _2O _3$, respectively.

Hence, only option C is true.

Leaching method is used to concentrate the ores of:

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

  1. Gold

  2. Silver

  3. Aluminium

  4. All of these

Show answer
Correct Option: D
Explanation:
Leaching
It involves treatment of ore with leaching agents (like NaOH, NaCN, KCN or other reagents) due to which ore becomes soluble and their impurities remain insoluble. The leaching Process is basically done in the extraction of Al from Alumina.
$Al _2O _3 + 2 NaOH \rightarrow 2NaAlO _2 +  H _2O$ + Impurities

If leaching process is done in case of Ag and Au with NaCN (0.4 to 0.8%) then the process is called as Mac-Arthur Forrest cyanide Process.
$Ag + NaCN \rightarrow NaAg(CN) _2 + $ Impurities
$Au + NaCN \rightarrow NaAu(CN) _2 + $ Impurities

In the leaching of gold by cyanide process, the following reaction takes place: 
$\displaystyle aAu+bKCN+cH _{2}O+dO _{2}\rightarrow eKAu(CN) _{2}+fKOH$
$\displaystyle uAu+vKCN+wH _{2}O+xO _{2}\rightarrow yKAu(CN) _{4}+zKOH$
Identify the correct statements with respect to the stoichiometric coefficients when these reactions are balanced using simplest natural numbers.

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

  1. $d, c, x, u$ are in anthmetic progression

  2. $c, y, w, b$ are in arithmetic progression

  3. $f, b, z, v$ are in geometic progressinon

  4. $d, c,a, b$ are geometnic progression

Show answer
Correct Option: A,B,D
Explanation:

$\displaystyle 4Au+8KCN+2H _{2}O+O _{2}\rightarrow 4KAu(CN) _{2}+4KOH$
$\displaystyle 4Au+16KCN+6H _{2}O+3O _{2}\rightarrow 4KAu(CN) _{4}+12KOH$
$a = 4$      $ b = 8$       $c = 2$      $ d = 1$        $e = 4$               $f = 4$
$u = 4$     $ v = 16$       $ w = 6$       $ x = 3$     $ y = 4$           $ z = 12$