Question

During Kjeldahi's method ammonia gas evolved is absorbed in $100$ml of $0.1$N $H_{2}S{O}_4$ solution this solution when titrated against $0.1$N NaOH solution required $60$ ml of NaOH calculate volume & normality of ammonium solution.

• A. 0.2 N
• B. 0.1 N
• C. 0.3 N
• D. 0.01 N

Answer 1

The correct option is B 0.1 N

${NH}_3$ evolved reacted with $H_2{SO}_4$ 100 ml , 0.1N,

${2NH}_3+H_2{SO}_4\rightleftharpoons {2NH}_4^{(+)}+{SO}_4^{-2}$

excess titrated with 60 ml, 0.1N $NaOH$.

$60\times 0.1=6$ millimoles ${OH}^{(-)}$

Hence 6 milli moles $H^{(-)}$ remained after reacting with ${NH}_3$

${NH}_3$ millimoles $=100\times 0.1-6=4$ millimoles

4 millimoles in $H^0$ ml 30 in remaining

$\left[{NH}_4^{+}\right]=\frac{4\times {10}^{-3}}{40\times {10}^{-3}}=0.1N$