Question

In Kjeldahl's method, nitrogen present is estimated as:

• A. $N_2$
• B. $N{H}_2$
• C. $N{O}_2$
• D. none of these

Answer 1

Answer: (B)

$N{H}_2$

Kjeldahl method is a method that is used the quantitatuin estimation of nitrogen conlaining in inorganic substances like $N{H}_3/N{H}_4^{+}$, and in organic substances.In kjeldah's method, notrogen is estimated in following steps :

$Step$ $1:$Degradation: Sample$+H_S{O}_4⟶{\left(N{H}_4\right)}_{2}S{O}_4+C{O}_2+S{O}_2+H_{2}O$

$Step$ $2:$ Ammonia is liberated : ${\left(N{H}_4\right)}_{2}S{O}_4+2NaOH⟶N{a}_{2}S{O}_4+2H_{2}O+2N{H}_3$

$Step$ $3:$ Ammonia is captured : $B{\left(OH\right)}_3+H_{2}O+N{H}_3⟶N{H}_4^{+}+B{\left(OH\right)}_4^{-}$

$Step$ $4:$ Back titration : $B{\left(OH\right)}_3+H_{2}O+N{a}_{2}C{O}_3⟶NaHC{O}_3+NaB{\left(OH\right)}_4+C{O}_2+H_{2}O$

Thus in Kjeldahl's method, nitrogen present is estimated as $N{H}_2$.