Subject

Chemistry

Class

NEET Class 12

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 Multiple Choice QuestionsShort Answer Type

41.

Calculate the number of Hions present in 1 mL of a solution whose pH is 10.


Given, pH = 10

[H+] = 1 x 10-10 mol/L

  Number of H+ ions in 1 L of solution
= 6.023 1023 1 X 10-10
= 6.023 x 1013
  Number of H+ ions in 1 mL of solution
= 6.023 X 1013 X 10-3
= 6.023 X 1010


42.

Write with a balanced chemical equation how gypsum is used for the conversion of ammonia into ammonium sulnate without using H2SO4 ?


When NH3 and CO2 are directly introduced into a gypsum slurry, ammonium sulphate is obtained. This method is called continental engineering process.

2NH3 + CaSO4·2H2O + CO2  (NH4)2SO4 + CaCO3                gypsum

CaCO3 is the byproduct of the reaction.


43.

Give the structure of pyrphyuric acid. How would you prepare it? What would you observe when colourless HI is added to pyrphuric acid ?


Pyrosulphuric acid is oleum. It is obtained when sulphur trioxide gas is passed through conc H2SO4 solution.

H2SO4 + SO3 H2SO2O7 98%                        oleum( or pyrosulphuric acid)

 The structure of pyrosulphric acid is

       

When colourless HI is added to pyrosulphuric acid, its colour becomes violet because pyrosulphuric acid oxidises I- to I2.

H2SO4 + 2HI     2H2O + SO2 + I2              colourless                         violet


44.

An organic compound 'A' on treatment with ammoniacal silver nitrate gives metallic silver and produces a yellow crystalline precipitate of molecular formula C9H10N4O4 on treatment with Brady's reagent. Give the structure of the organic compound 'A'.


Since the organic compound 'A' reduces ammoniacal silver nitrate (Tollen's reagent), it must be an aldehyde. Moreover, with Brady's reagent (2, 4-dinitro phenyl hydrazine) it gives a precipitate of molecular formula C9H10N4O4 it must be propanal (CH3CH2CHO). The reactions are as follows


45.

Convert phenol to p-hyroxy acetophenone in not more than 2 steps.