Question

in an organic compound of molecular mass greater than 100 containing only C,H,N the % of C is 6 times that of Hwhile sum of Cand H is 1.5 times % of N what will be minimum molecular mass
a)175
b) 140
c) 105
d)210​

Answer 1

Answer:

Let the compound be C  

x

​  

H  

y

​  

N  

z

​  

.

Mass of C=12x

Mass of H=y

Mass of N=14z

Total Mass =12x+y+14z

Mass % of C=  

(12x+y+14z)

12x

​  

×100

Now given,

(I) Mass % of C=6× mass % of H

   ⟹12x=6y

   ⟹y=2x

(II) Mass % of C+ Mass % of H=1.5 (mass % of N)

    ⟹12x+y=1.5×14z

     ⟹12x+2x=21z

   ⟹x=1.5z

and y=3z.

So, the compound can be expressed as C  

1.5z

​  

H  

3z

​  

N  

z

​  

 or C  

3z

​  

H  

6z

​  

N  

2z

​  

.

Now choosing, z=1, we have C  

3

​  

H  

6

​  

N  

2

​  

.

Molecular weight = 3×12+6×1+2×14=70 g/mol

Given molecular weight >100.  

So, when we choose z=2, we have C  

6

​  

H  

12

​  

4

​  

.

Molecular weight = 6×12+12×1+4×14=140 g/mol which is greater than 100

Explanation:

so the answer is B 140

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