Asbestos [NCERT one shot for NEET/JEE]

 

Silicates

A large number of silicates minerals exist in

nature. Some of the examples are feldspar,

zeolites, mica and asbestos. The basic

structural unit of silicates is [SiO4]^4– (Fig.11.7)

in which silicon atom is bonded to four

oxygen atoms in tetrahedron fashion. In

silicates either the discrete unit is present or

a number of such units are joined together

via corners by sharing 1,2,3 or 4 oxygen

atoms per silicate units. When silicate units

are linked together, they form chain, ring,

sheet or three-dimensional structures.

Negative charge on silicate structure is

neutralised by positively charged metal ions.

If all the four corners are shared with other

tetrahedral units, three-dimensional network

is formed.

Two important man-made silicates are

glass and cement.

 Question:  From NCERT  | NEET   ||| [Difficult level:Easy] Helpful? Yes. Share and spread a word. 

.Platinized asbestos used as a catalyst in the manufacture of H2SO4 is an example of:
.1. heterogeneous catalyst                   
2. auto-catalyst
3. homo-catalyst                                 
4. induced catalyst

Answer:1. heterogeneous catalyst   

A catalyst is a substance which enhances the rate of a chemical reaction without
itself getting used up in the reaction. The phenomenon using catalyst is known as
catalysis. In homogeneous catalysis, the catalyst is in the same phase as are the
reactants, and in heterogeneous catalysis the catalyst is in a different phase from
that of the reactants.

Heterogeneous catalysis: Adsorption of reactants on the solid

surface of the catalysts increases the rate of reaction. There are

many gaseous reactions of industrial importance involving solid

catalysts. Manufacture of ammonia using iron as a catalyst,

manufacture of H2SO4 by contact process and use of finely divided

nickel in the hydrogenation of oils are excellent examples of

heterogeneous catalysis.

The catalytic process in which the reactants and the catalyst are in

different phases is known as heterogeneous catalysis. Some of the

examples of heterogeneous catalysis are given below:

(i) Oxidation of sulphur dioxide into sulphur trioxide in the

presence of Pt.

Pt(s)

2SO₂ (g) +Pt(s)→ 2SO₃ (g) 2

The reactant is in gaseous state while the catalyst is in the

solid state.

(ii) Combination between dinitrogen and dihydrogen to form

ammonia in the presence of finely divided iron in Haber’s process

The reactants are in gaseous state while the catalyst is in the

solid state.

 Question:  100% NCERT covered from Particular Keyword.Explanations are 100% from NCERT | [Difficult level: Easy] From NCERT NEET Derived Question.

Which of the following catalyst is used for the following

conversion ?

(a) Platinized Asbestos (b) Red hot iron tube

(c) Platinized Nickel (d) Iron-molybdenum

Answer:b

 Question:  100% NCERT covered from Particular Keyword.Explanations are 100% from NCERT | [Difficult level: Easy] From NCERT NEET Derived Question.

In the Haber process for the manufacture of ammonia the

following catalyst is used

(a) Platinized asbestos

(b) Iron with molybdenum as promoter

(c) Copper oxide

(d) Alumina

Answer:b 

 Haber’s process, ammonia is manufactured from N 2 and H 2using iron as catalyst with molybdenum as promoter at high temperature and pressure

 Question:  100% NCERT covered from Particular Keyword.Explanations are 100% from NCERT | [Difficult level: Easy] From NCERT NEET Derived Question.

Read the following statements regarding enzyme catalysis

(i) Enzyme catalysis is highly specific in nature.

(ii) Enzyme catalysis to work effectively requires optimum

temperature (298-310 K) and optimum pH (3-5)

(iii) Metal ions like Na+, Mn2+, Co2+, Cu2+ etc. increases

the activity of enzymes.

(iv) Catalyst used in Ostwald’s process is platinised

asbestos at 673 K.

(v) Catalyst used in contact process is platinised asbestos

or V2O5 at 673-723 K.

Which of the following is the correct coding for the above

statements?

(a) FTFTF (b) TFTFT

(c) TTFFF (d) FTTFT

Answer:b  

 Optimum pH for the enzyme catalysis is 5-7. 

Catalyst used in Ostwald’s process is platinised asbestos at 573 K.