Confusing but Frequently Asked MCQs of Chemistry.

   Chemistry Frequently Asked MCQs For MBBS/BDS/NEET/Paramedicals/Applied Sciences.

     

  Set 1 Chemistry

11.  The V.D. of X is 4 times of Y. If molecular wt. of X is M then that of Y is

a.      M                           

b.       M/2

c.        4M                                    

d.       M/4

22.   Radioactivity is :

a.      Zero order                       

b.       1^st order

c.       2^nd order                          

d.      3^rd order

33. Which of the following is the most basic compound:

a.      Acetanilide

b.      P-nitro aniline

c.       Benzylamine

d.      Aniline

44.The compound [Fe(CN)₆]^4-  has hybridization

a.      sp²

b.      sp³

c.       sp³d²

d.      sp

55. When NH₄Cl is added to NH₄OH, its pH:

a.      Decreases

b.      Remains unchanged

c.       Increases

d.      Zero

66.   In the following equilibrium

HCl + H₂O              H₃O⁺ + Cl^- 

H₂O is a base according to the:

a.      Classical concept

b.      Arrhenius concept

c.       Bronsted-Lowry concept

d.      Lewis concept

77.   Which of the following when reacted with water produces phenol?

a.      C₆H₅N-NCl

b.      C₆H₅-Cl

c.       C₆H₅CH₂Cl

d.      C₆H₅-CHO

88.   Tear gas is :

a.      Chloretone

b.      Ethyl carbonate

c.       Chloropicrin

d.      Methylene chloride

99.  pH of 0.001 M HCl is:

a.      1

b.      2

c.       3

d.      0

    10.Max. no. of electrons in d subshell is:

a.      2

b.      6

c.       10

d.      14

111.  In which of the following compounds does hydrogen have negative valency?

a.      NH₃

b.      H₂O

c.       HCl

d.      NaH

112.  Amount of H₂SO₄ present in 500 cc. of 1.5 N H₂SO₄ soln. is

a.      4.9 gm

b.      49 gm

c.       24.8 gm

d.      36.75 gm

113.  Treatment of 1-phenylethanone with hydrazine in presence of sodium hydroxide produces ethyl benzene. This reaction is known as:

a.      Wolf kishner reduction

b.      Aldol condensation

c.       Clasien condensation

d.      Williamson's synthesis

114.  Which of the following contains 6x10²² atoms?

a.      12 gm of C

b.      3.2 gm of S

c.       24 gm of Mg

d.      36 gm of oxygen

115.  What is the correct order of electro negativity of the following halogens?

a.      Cl>Br>I>F

b.      F>Br>I>Cl

c.       F>Cl>Br>I

d.      Cl>F>I>Br

116.  75% of a 1^st order rxn. was completed in 32 min, when was 50% of the rxn. completed?

a.      24 min

b.      16 min

c.       8 min

d.      4 min

                    Hints And Solutions

1.  VDx=4X, VDy=X, Mx=M, My=?

M.W. = 2 X V.D.

Mx/My = VDx/VDy

My = Mx.VDy/VDx = M X x/4x = M/4

2.  Radioactive decay is 1^st order reaction

3.  Benzylamine

4.  sp³d²  

5.  Decreases

NH₄OH               NH₄⁺ + OH^-

NH₄Cl            NH₄⁺ + Cl^-

When NH₄Cl is added to NH₄OH soln., the above equilibrium will shift towards left because of high concentration of common ion (NH₄⁺) and thus the ionization of NH₄OH is further suppressed and pH decrease.

6.  Bronsted-Lowry concept

According to this concept, an acid is a proton donor and a base is the proton acceptor molecule.

7.  C₆H₅N-NCl

8.  Chloropicrin is used in tear gas.

CHCl₃  + conc. HNO₃             CCl₃-NO₂    +   H₂C

Chloroform                            Chloropicrin

9.  pH = -log[H⁺] = -log[0.001] = -log10^-3 = 3

10.  s :2, p ;6, d:10, f :14

11.  Oxidation no. of hydrogen is always +1 except in metal hydrides (LiH, NaH, CaH₂).In metal hydrides hydrogen exhibits -1 oxidation no.

12.  Normality (N) = No. of equivalent / volume in liter

or,          1.5     =  x X 1000

                              49 X 500

or,  3/2 X  49   = 2x

or,  3X49 / 4    = x

 or,            x      =    36.75 gm

13.  Wolf kishner reduction: reduction of carbonyl compounds to alkanes by using hydrazine and KOH (alkaline soln.)

14.  32 gm of S contains = 6 X 10²³ atoms of S

3.2 gm of S contains = (6X10²³X3.2)/32

                                     =  6X10²² atoms

15.  c. F>Cl>Br>I

    The value of electronegativity decreases down the group.

16.  b. 16 min

t_50% = t_1/2                  t_75% = 2t_1/2