Chapter-6 General Principles and Processes of Isolation of Elements

On heating compound (A) gives a gas (B) which is a constituent of air. This
gas when treated with 3 mol of hydrogen (H2) in the presence of a catalyst
gives another gas (C) which is basic in nature. Gas C on further oxidation in
moist condition gives a compound (D) which is a part of acid rain. Identify
compounds (A) to (D) and also give necessary equations of all the steps involved.

On heating lead (II) nitrate gives a brown gas “A”. The gas “A” on cooling
changes to colourless solid “B”. Solid “B” on heating with NO changes to a
blue solid ‘C’. Identify ‘A’, ‘B’ and ‘C’ and also write reactions involved and
draw the structures of ‘B’ and ‘C’.

An amorphous solid “A” burns in air to form a gas “B” which turns lime water
milky. The gas is also produced as a by-product during roasting of sulphide
ore. This gas decolourises acidified aqueous KMnO4 solution and reduces
Fe3+ to Fe2+. Identify the solid “A” and the gas “B” and write the reactions
involved.

Phosphorus forms a number of oxoacids. Out of these oxoacids phosphinic
acid has strong reducing property. Write its structure and also write a reaction
showing its reducing behaviour.

Give an example to show the effect of concentration of nitric acid on the
formation of oxidation product.

Phosphorus has three allotropic forms — (i) white phosphorus (ii) red
phosphorus and (iii) black phosphorus. Write the difference between white
and red phosphorus on the basis of their structure and reactivity.

Name three oxoacids of nitrogen. Write the disproportionation reaction of that
oxoacid of nitrogen in which nitrogen is in +3 oxidation state.

White phosphorus reacts with chlorine and the product hydrolyses in the
presence of water. Calculate the mass of HCl obtained by the hydrolysis of the
product formed by the reaction of 62 g of white phosphorus with chlorine in
the presence of water.

Explain why ozone is thermodynamically less stable than oxygen.

Explain

On reaction with Cl2, phosphorus forms two types of halides ‘A’ and ‘B’. Halide
A is yellowish-white powder but halide ‘B’ is colourless oily liquid. Identify A
and B and write the formulas of their hydrolysis products.

Give reason to explain why ClF3 exists but FCl3 does not exist.

Why is nitric oxide paramagnetic in gaseous state but the solid obtained on
cooling it is diamagnetic?

In PCl5, phosphorus is in sp3d hybridised state but all its five bonds are not
equivalent. Justify your answer with reason.

PH3 forms bubbles when passed slowly in water but NH3 dissolves. Explain
why?

Write the structure of pyrophosphoric acid

Write a balanced chemical equation for the reaction showing catalytic oxidation
of NH3 by atmospheric oxygen.

Write a balanced chemical equation for

Explain the following :
(a) CO2 is a better reducing agent below 710K whereas CO is a better reducing
agent above 710K.
(b) Generally sulphide ores are converted into oxides before reduction.
(c) Silica is added to the sulphide ore of copper in the reverberatory furnace.
(d) Carbon and hydrogen are not used as reducing agents at high
temperatures.
(e) Vapour phase refining method is used for the purification of Ti.

Match items of Column I with the items of Column II and assign the correct
code :
Column I                                          Column II
(A) Cyanide process                            (1) Ultrapure Ge
(B) Froth Floatation Process                  (2) Dressing of ZnS
(C) Electrolytic reduction                      (3) Extraction of Al
(D) Zone refining                               (4) Extraction of Au
                                                      (5) Purification of Ni

Code :
(i) A (4) B (2) C (3) D (1)
(ii) A (2) B (3) C (1) D (5)
(iii) A (1) B (2) C (3) D (4)
(iv) A (3) B (4) C (5) D (1)

Match the items of Column I with the items of Column II and assign the correct
code :
Column I                                                   Column II
(A) Coloured bands                                     (1) Zone refining 
(B) Impure metal to volatile complex              (2) Fractional distillation
(C) Purification of Ge and Si                         (3) Mond Process
(D) Purification of mercury                           (4) Chromatography
(5) Liquation

Code :
(i) A (1) B (2) C (4) D (5)
(ii) A (4) B (3) C (1) D (2)
(iii) A (3) B (4) C (2) D (1)
(iv) A (5) B (4) C (3) D (2)

Match the items of Column I with the items of Column II and assign the correct
code :
Column I                                          Column II
(A) Coloured bands                             (1) Zone refining
(B) Impure metal to volatile complex        (2) Fractional distillation
(C) Purification of Ge and Si                    (3) Mond Process
(D) Purification of mercury                      (4) Chromatography
(5) Liquation

Write the chemical reactions involved in the extraction of gold by cyanide
process. Also give the role of zinc in the extraction.

Give two requirements for vapour phase refining.

Write down the reactions taking place in Blast furnace related to the metallurgy
of iron in the temperature range 500-800 K.

How are metals used as semiconductors refined? What is the principle of the
method used?

What is the role of flux in metallurgical processes?

Which method is used for refining Zr and Ti? Explain with equation.

Why is sulphide ore of copper heated in a furnace after mixing with silica?

The mixture of compounds A and B is passed through a column of Al2O3 by
using alcohol as eluant. Compound A is eluted in preference to compound B.
Which of the compounds A or B, is more readily adsorbed on the column?

The purest form of iron is prepared by oxidising impurities from cast iron in
a reverberatory furnace. Which iron ore is used to line the furnace? Explain
by giving reaction.

How do we separate two sulphide ores by Froth Floatation Method? Explain
with an example.

Although carbon and hydrogen are better reducing agents but they are not
used to reduce metallic oxides at high temperatures. Why?

Write two basic requirements for refining of a metal by Mond process and by
Van Arkel Method.

How is copper extracted from low grade copper ores?

Wrought iron is the purest form of iron. Write a reaction used for the
preparation of wrought iron from cast iron. How can the impurities of sulphur,
silicon and phosphorus be removed from cast iron?

At temperatures above 1073K coke can be used to reduce FeO to Fe. How can
you justify this reduction with Ellingham diagram?

Why is an external emf of more than 2.2V required for the extraction of Cl2 from
brine?

What is slag?

Which is better reducing agent at 983K, carbon or CO?

At which temperature carbon can be used as a reducing agent for Foe ?

What is the role of graphite rods in electrometallurgy of aluminium ?

What is the role of cryolite in electrometallurgy of aluminium?

What are depressants?

Copper can be extracted by hydrometallurgy but not Zn. Why?

Give name and formula of important ore of iron .

Give name and formula of important ore of Copper .

Give name and formula of important ore of Zinc .

Describe the method of refining of nickel

What is Zone Refining? Explain with example

Write principal of electro-refining.the 

Describe the method of refining of Zirconium and Titanium.

Out of C & CO, which is better reducing agent for ZnO?

Why copper matte is put in silica lined converter?

What is meant by term chromatography?

Why is reduction of metal oxide easier if metal formed is in liquid state at temperature of reduction. 

(i) Zinc but not copper is used for recovery of Ag from the complex [Ag(CN)2]-. (ii) Partial roasting of sulphide ore is done in the metallurgy of copper.

(iii) Extraction of Cu from pyrites is difficult than that from its oxide ore through reduction.

Explain the method for obtaining pig iron from magnetite.

Describe the principles of extraction of copper from its ore . 

Name the principal ore of aluminium and describe how Al is extracted from its ore.

Describe the principles of extraction of Zinc from zinc blende .

What is the role of cryolite in the metallurgy of aluminium?

Why copper matte is put in silica lined converter?

Differentiate between "minerals" and "ores".

How is 'cast iron' different from 'pig iron"?

Giving examples, differentiate between 'roasting' and 'calcination'.

How can you separate alumina from silica in bauxite ore associated with

silica? Give equations, if any.

Describe a method for refining nickel.

Predict conditions under which Al might be expected to reduce MgO.

Outline the principles of refining of metals by the following methods:

(i) Zone refining

(ii) Electrolytic refining

(iii) Vapour phase refining

What is the role of graphite rod in the electrometallurgy of aluminium?

Name the processes from which chlorine is obtained as a by-product. What

will happen if an aqueous solution of NaCl is subjected to electrolysis?

The choice of a reducing agent in a particular case depends on

thermodynamic factor. How far do you agree with this statement? Support

your opinion with two examples.

Out of C and CO, which is a better reducing agent for ZnO ?

The value of  for formation of Cr₂O₃ is - 540 kJmol^-1 and that of Al₂ O₃ is - 827 kJmol^-1. Is the reduction of Cr₂O₃ possible with Al?

Why is zinc not extracted from zinc oxide through reduction using CO?

How is leaching carried out in case of low grade copper ores?

What criterion is followed for the selection of the stationary phase in

chromatography?

What is meant by the term "chromatography"?

State the role of silica in the metallurgy of copper.

Write chemical reactions taking place in the extraction of zinc from zinc blende.

Write down the reactions taking place in different zones in the blast furnace

during the extraction of iron.

Name the common elements present in the anode mud in electrolytic refining

of copper. Why are they so present ?

Out of C and CO, which is a better reducing agent at 673 K?

Explain: (i) Zone refining (ii) Column chromatography.

Why is the extraction of copper from pyrites more difficult than that from its

oxide ore through reduction?

What is the role of depressant in froth floatation process?

The reaction,

is thermodynamically feasible as is apparent from the Gibbs energy value.

Why does it not take place at room temperature?

What is the significance of leaching in the extraction of aluminium?

Which of the ores mentioned in Table 6.1 can be concentrated by magnetic separation method?