NCERT Class XI Chemistry Organic Chemistry Some basic principles and Techniques Solutions

Question : 33

Total: 40

A sample of 0.50 g of an organic compound was treated according to Kjeldahl’s method. The ammonia evolved was absorbed in 50 mL of 0.5 M H2SO4. The residual acid required 60 mL of 0.5 M solution of NaOH for neutralisation. Find the percentage composition of nitrogen in the compound.

Solution:

Given : Mass of compound taken = 0.50 g; Vol. of H2SO4 = 50 mL
Molarity of H2SO4 = 0.5 M; Vol. of NaOH required = 60 mL
Molarity of NaOH required = 0.5 M
Method adopted : Kjeldahl’s method
Formula used : % of N =

1.4×M×2[V−

]

... (i)
M = 0.5 M (Molarity of H2SO4), V = 50 mL, V1 = 60 mL
m = 0.5 g (mass of compound)
By substituting the values in the formula, we get,
% of N =

1.4×0.5×2(50−

)

0.5

= 56
∴ % of N in the given compound = 56%

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