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

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Question : 33 of 40
Marks: +1, -0
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\mathrm{H_2SO_4}. 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\mathrm{H_2SO_4} = 50 mL
Molarity of H2SO4\mathrm{H_2SO_4} = 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−V12]m\frac{1.4 \times M \times 2\left[V - \frac{V_1}{2}\right]}{m} ... (i)
M = 0.5 M (Molarity of H2SO4\mathrm{H_2SO_4}), V = 50 mL, V1V_1 = 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(50−602)0.5\frac{1.4 \times 0.5 \times 2\left(50 - \frac{60}{2}\right)}{0.5} = 56
∴ % of N in the given compound = 56%
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