In Kjeldahl's method, 0.4422 g of an organic compound was digested with conc. H_(2)SO_(4). The ammonia evolved on distilling the resulting solution with excess of NaOH solution was absorbed in 50 mL of 1 N H_(2)SO_(4) solution. The residual acid required 65.5 mL of N//2 alkali solution for complete neutralisation. Find the percentage of nitrogen in the given organic compound.

In Kjeldahl's method, 0.4422 g of an organic compound was digested wit

1.	In Kjeldahl's method, 0.4422 g of an organic compound was digested with conc. H_(2)SO_(4). The ammonia evolved on distilling the resulting solution with excess of NaOH solution was absorbed in 50 mL of 1 N H_(2)SO_(4) solution. The residual acid required 65.5 mL of N//2 alkali solution for complete neutralisation. Find the percentage of nitrogen in the given organic compound.
Answer» Solution :Calculation of the volume of UNUSED acid. volume of `NaOH` solution =65.5 mL Normality of `NaOH` solution `=1//2 N` Normality of `H_(2)SO_(4)` solution `= 1 N` Volume of the acid can be calculated by applying normality equation, `ubrace(N_(1)V_(1))_("Acid")= ubrace(N_(2)V_(2))_("Base")` `(1N)xxV_(1)=(1//2N)xx(65.5 mL), V_(1)=((1//2N)xx(65.5 mL))/((1N))=32.75 mL` STEP II. Calculation of the volume of acid used volume of `H_(2)SO_(4)` added =50 mL Volume of `H_(2)SO_(4)` left unused =32.75 mL `:.` Volume of `H_(2)SO_(4)` used `= (50-32.75)=17.25 mL` Step III. Calculation of the percentage of nitogen Mass of COMPOUND =0.4422 G Volume of `H_(2)SO_(4)` used =17.25 mL Normality of `H_(2)SO_(4)` used = 1 N Percentage of `N=(1.4 xx" Volume of acid used"xx"Normality of acid used")/("Mass of the compound")` `=(1.4xx17.25xx1)/0.4422=54.61 %`