Some Basic Concepts of Chemistry - Online Test

Answer : Option A
Explaination / Solution:

Molar mass

=Σ  [ 2  x  ( atomic mass of  Al )  ,  3  x ( atomic mass of O ) ]u 

=  [(2X27)+(3X16)]u$$

= ( 54  + 48 ) u

= 102 u. 

Answer : Option A
Explaination / Solution:

Molar massof  C6 H10 O5

=  Sum of the atomic masses of  six  C atoms  ,  ten  H  atoms  &   six  O  atoms

thus , substituting the required atomic masses  of

 C= 12 ,

H = 1 , &

 O = 16 ,

  we get ,

Molar mass   of  C6 H10 O5 

 = [ 6(12)+10(1)+5(16) ] u

= (72  +  10   +  80 ) u

=162 u

Answer : Option D
Explaination / Solution:

Molar mass of    Ag NO3  

 =    [  atomic mass of Ag     +  atomic mass of  N   +   3  (   atomic mass of O ) ) ]  u

Substituting the atomic masses of  Ag ,  N   &  O  as   107.9 , 14  &  16  ,respectively in the above expression  we get -  

  =  [107.9+14+(3X16)]$$

=169.9 u

Answer : Option C
Explaination / Solution:

The problem is based upon the concepts of Avogadro's law

.Accordingly   ,  one mole  (ie  18 g )  of water   contains  

 = 6.02 x 1023 molecules of water

. Again , since the number of  oxygen atoms in one molecule of water ( H2 O ) 

 =    1  atom 

∴$\therefore$ the number of oxygen atoms in 6.02  x 1023 molecules of water

.=    6.02 x 1023   atoms 

Answer : Option B
Explaination / Solution:

Since,18g H2O

= 1mol water containing 6.02 x 1023 molecules of water  (H2O )

   &   the number of H atoms in 1 molecule of  hydrogen (H2)  =  2

∴$\therefore$ the number of H atoms in 6.02 x 1023 molecules

= (6.02 x 1023 x 2)

=1.204 x 1024.

Answer : Option C
Explaination / Solution:

 Since , 1 m

=1000 mm.

 or,  1 mm

 =  11000m

∴$\therefore$2000 mm  

=[ 11000X2000]  m

=   2 m

Answer : Option C
Explaination / Solution:

Since ,  1L

= 1000mL  

   or , 1mL

 =11000L .

∴$\therefore$  0.05mL

=  11000X0.05L  

=  0.00005 L .

Answer : Option C
Explaination / Solution:

Since ,  Molarity

= [molesofsolute∗volumeofsolution(mL)X1000]M

∴$\therefore$   substituting the given values  , we get -

 Molarity ( M )

=  0.10250X1000M

=0.4M

* moles of solute ie.  NaOH =440 mole

.= 0.1mol

Answer : Option D
Explaination / Solution:

The occurance of a chemical reaction is always associated with breaking & formation of bonds of the reactant and products along with rearrangement of their atoms , hence the statement at option 1 is most appropriate. ie. " Whenever there is a rearrangement of atoms which makes or breaks chemical bonds a chemical reaction takes place."

Answer : Option B
Explaination / Solution:

Since ,as per Avogadro's  law ,

the  mass of 6.02 x 1023 molecules of O2

= 32 g

∴$\therefore$ mass of 1 molecule of  O2 

= 326.022X1023g 

= 5.32 x 10−23 g