VITEEE 2015 :: Chemistry :: General questions

• Chemistry - General questions

 A compound X  on heating gives a colourless gas. The residue is dissolved in water to obtain Y. Excess CO₂ is passed through aqueous solution of Y when Z  is formed. Z on gentle heating gives back X  . The compound X is 

Answer:

Explanation:

$CaCO_{3}$  $\underrightarrow{\triangle}$ $CaO+CO_{2}\uparrow$

   X                                   colourless gas

 $ CaO+H_{2}O\rightarrow Ca(OH)_{2}$

  Residue                        Y

$ Ca(OH)_{2}+2CO_{2}\rightarrow  Ca(HCO_{3})_{2}$

   Y             excess                      Z

$ Ca(HCO_{3})_{2}$  $\underrightarrow{\triangle}$   $ CaCO_{3}+CO_{2}\uparrow+H_{2}O$

    Z                                      X

 Caffeine has a molecular weight of 194 u. If it contains 28.9% by mass of nitrogen, the number of atom of nitrogen in one molecule of caffeine is 

Answer:

Explanation:

 M. wt. of caffeine =194 u

 % of N present in one molecular of caffeine is 28.9% of 

$194 u= \frac{28.9}{100}\times194=56 u$

 Mass of one N atom =14 m

 =1N atom (  $\because$ 14 m=14 u)

$\therefore$     $56 u=\frac{56}{14}$  N atom =4 N atom

The IUPAC  name of  

is 

Answer:

Explanation:

The correct IUPAC name is 7-ethyl-2,4,5,6-tetramethyldeca-1,8-diene

A colourless water-soluble solid A on heating gives equimolar quantities of B and C  . B gives dense white fumes with HCl and C does so with  NH₃. B gives a brown precipitate with Nessler's reagent and C gives a white precipitate with nitrates of Ag⁺, Pb⁺ and Hg⁺. A is 

Answer:

Explanation:

$NH_{4}Cl $   $\underrightarrow{\triangle}$ $NH_{3}+HCl$

A(colourless)                        B     & C ( equimolar quantities)

$NH_{3}+HCl \rightarrow NH_{4}Cl $

 B                         dense white fumes

 $NH_{3}+2K_{2}[HgI_{4}]+3KOH \rightarrow H_{2}NHgO.HgI+7KI+H_{2}O$

                Nessler's reagent                               Brown ppt. Iodine of Milinon's base

$HCl+MNO_{3}\rightarrow MCl+HNO_{3}$

  C                                 white ppt.

                                     (M= Ag⁺, Pb²⁺, Hg⁺)

The false  statements among the following are

I. A primary carbocation is less stable than a tertiary carbocation

II.  A secondary propyl carbocation is less stable than allyl carbocation

III.   A tertiary free radical is more stable than a primary free radical

IV.  Isopropyl carbanion is more stable than ethyl carbanion

Answer:

Explanation:

Since 2° propyl carbocation  is little more stable than allyl carbocation  and ethyl carbanion is more stable than isopropyl carbanion

• Chemistry - General questions