1 ) The molarity of a 0.2 N Na2CO3 solution will be : -
A ) 0.1 M , B
) 0.2 M ,
C ) 0.3 M , D
) None of these ,
Correct
Answer : - A ) 0.1 M ,
Solution : -
2 )
The equivalent weight of a certain trivalent element is 20 . Molecular weight
of its oxide is : -
A ) 150 , B
) 168 ,
C ) 189 , D ) None of these ,
Correct
Answer : - B ) 168 ,
3 )
There are two isotopes of an element with atomic mass Z . Heavier one has
atomic mass ( Z + 2 ) and lighter one has atomic mass ( Z – 1 ) , then
abundance of lighter one is : -
Solution
: -
( Z + 2 ) ( x )
+ ( Z – 1 )( 1 – x ) =
Z ,
Zx + 2x – Zx + Z – 1 + x = Z ,
So , x = 1 / 3 .
So , ( Z + 2
) =
( 1 / 3 ) x 100 = 33.3 %
.
And ( Z – 1 ) = 1 –
33 % =
67.6 % .
4
) In an acidic medium dichromate ion
oxidizes ferrous ion to ferric ion . If the gram molecular mass of potassium
dichromate is 294 g , its equivalent mass is : -
A ) 46 , B
) 49 ,
C ) 55 , D
) None of these ,
Correct
Answer : - B ) 49 ,
Solution
: -
Fig
Oxidation charge on ( Cr ) = 6 – 3 = 3 .
For two Cr atoms = 3 x 2
= 6 .
Equivalent weight
= molecular weight /
n = 294 / 6
= 49 .
5
) What is concentration of nitrate ions
, if equal volumes of 0.1 M AgNO3
and 0.1 M NaCl are mixed together ?
A ) 0.01 , B
) 0.05 ,
C ) 0.12 , D
) None of these ,
Correct
Answer : - B ) 0.05 ,
Solution
: -
AgNO3
--------> Ag+ +
NO3- .
So , AgNO3 has 2 ions
= 0.1 / 2 = 0.05
, Answer .
