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 `H_(2)SO_(4)`. The residual acid required 60 mL of 0.5 M solution of NaOH for neutralisation. What would be the percentage composition of nitrogen in the compound?

Explanation

60ml of 0.5 M NaOH solution `=(60)/(2)` ml of 0.5M `H_(2)SO_(4)`
=30 ml of M `H_(2)SO_(4)` solution
Volume of 0.5 M `H_(2)SO_(4)~ used =50-30=20ml
Now, 20 ml of 0.5 M `H_(2)SO_(4)=2xx20ml` of 0.5 M `NH_(3)`
1000 ml of 1M `NH_(3)` contain 14g
1000 ml of 0.5 M `NH_(3)` contain 7g
40 ml of 0.5 M `NH_(3)~ contain `(7)/(1000)xx40g`
`% "of" N=(7xx40)/(1000xx0.50)xx100=56%`