In the Kjeldahl's method for estimation of nitrogen present in a soil sample, ammonia evolved from 0.75 g of sample neutralized 10 mL of 1 M ${\mathrm{H}}_2{\mathrm{SO}}_4$. The percentage of nitrogen in the soil is

${\mathrm{H}}_2{\mathrm{SO}}_4+2{\mathrm{NH}}_3⟶{\left({\mathrm{NH}}_4\right)}_2{\mathrm{SO}}_4$

$10 \mathrm{mL}\text{ of }1{\mathrm{MH}}_2{\mathrm{SO}}_4=10\mathrm{mmol} \left[\mathrm{M}\times {\mathrm{V}}_{\left(\mathrm{mL}\right)}=\mathrm{mmol}\right]$

${\mathrm{NH}}_3\text{ consumed }=20\mathrm{mmol}$

$\mathrm{Acid} \mathrm{used} \mathrm{for} \mathrm{the} \mathrm{absorption} \mathrm{of} \mathrm{ammonia}$

$=20-10\mathrm{mmol}$

$=10 \mathrm{mL}\text{ of }2 \mathrm{N}\text{ (or }1\mathrm{M}){\mathrm{H}}_2{\mathrm{SO}}_4$

$\%\text{ of }\mathrm{N}=\frac{1.4\times \mathrm{N}\times \mathrm{V}}{\mathrm{W}}=\frac{1.4\times 2\times 10}{0.75}=37.33\%$