A sample of 0.50 gm of an organic compound was treated according to Kjeldahl's method the smmonia evolved was absorbed in 50 ml of `0.5MH_2SO_4`. The residual acid required 60 cm of 0.5M solution of `NaOH` for neutralisation. Find the percentage composition of nitrogen in the compound.

Explanation

Mass of organic compound taken `= 0. 50` g
Vol. of `0.5 M H_2 SO_4` taken `= 50` mL
The residual acid required 60 mL of 0.5 M solution of NaOH for neutralisation
60 mL of 0.5 M NaOH solution
`-= (60)/(2)` mL of `0.5 M H_2 SO_4` solution
`-= 30` mL of `0.5 M H_2 SO_4` solution
Volume of 0.5 `M H_2 SO_4` used `= 50- 30= 20` mL
Now
20 mL of `0.5 M H_2 SO_4 -= 2 xx 20` mL of `0.5 M NH_3` solution
or `= 40` mL of `0.5 M NH_3` solution
1000 mL of 1 M `NH_3` contain nitrogen `= 14` g
40 m L of `0.5 M NH_3` contain nitrogen `= (14 x 40xx 0.5)/(1000)`
% of `N = ( 14 xx 40 xx 0.5)/(1000 xx 0.50) xx 100`
`= 56%`