MHT CET 2018 :: Chemistry :: General questions

• Chemistry - General questions

Which of the following polymers is used to manufacture clothes for firefighters?

Answer:

Explanation:

Nomex is a flame-resistant polymer and it is used to manufacture clothes for firefighters.It is prepared by condensation of

m-phenylenediamine and isopthalamide monomers.

 . Thiokol is obtained by the condensation co-polymerisation of ethylene dichloride and sodium tetrasulphide (Na₂ S₄). It is used as binder in solid rocket fuel.

. Kevlar is obtained by condensation co-polymerisation of terephthalic acid and 1,4- diaminobenzene.It is used for making bulletproof vests.

.  Dynel is a copolymer of acrylonitrile and vinyl chloride monomers.It is used for making synthetic hair wigs.

What is the density of the solution of sulphuric acid as an electrolyte in the lead accumulator?

Answer:

Explanation:

An aqueous solution of sulphuric acid i.e, 38% by weight or having a density of 1.30 g mL-1is used as an electrolyte in lead accumulators,It is consumed during discharging and when  the concentration of H₂SO₄ falls to 1.20 g mL^-1 , it requires recharging.Thus, the most suitable option is (b)

 Excess of ammonia  with sodium hypochlorite solution  in presence of glue  or gelatin gives 

Answer:

Explanation:

 Excess of ammonia  (NH₃)  when reacts with sodium hypochlorite solution (NAOCl)  in presence of glue or gelatin gives hydrazine  (NH₂.NH₂) . This process is known as the Raschig process.

$2NH_{3}+NaOCl\rightarrow N_{2}H_{4}+NaCl+H_{2}O$

 The addition of gelatin or glue suppress the side reaction by complexing with the metal ions and the yield of hydrazine is increased

Phenol in presence of sodium hydroxide reacts with chloroform to form salicylaldehyde. This reaction is known as

Answer:

Explanation:

 In case of the Reimer-Tiemann  reaction, phenol reacts with chloroform in presence of sodium hydroxide followed  by acid hydrolysis to give salicylaldehyde as the major product,

Bauxite, the ore of aluminium, is purified by which process?

Answer:

Explanation:

 (i) Hall's process is the major industrial process for smelting aluminium.It involves dissolving aluminium oxide in molten cryolite and electrolysing the molten salt bath.

(ii)  Hoope's process or electrolytic refining is used to refine the obtained aluminium metal which is not 100% pure.

(iii)  Mond's  process is used to refine nickel

(iv)  Liquation  process  is used to refine  a metal with low melting point like tin, bismuth, lead , mercury etc.

 Thus, option (b) is correct.

• Chemistry - General questions