For the estimation of nitrogen, 1.4 g of an organic compound was digested by Kjeldahl method and the evolved ammonia acid absorbed in 60 mL of `M/10` sulphuric acid. The unreacted acid required 20 mL of `M/10` sodium hydroxide for complete neutralization. the percentage of nitrogen in the compound is

Options

A. 0.06
B. 0.1
C. 0.03
D. 0.05

Answer

B

Explanation

Mass of organic compound = 1.4 g, let it contain X m mole of N atom.
organic compound `to underset("X m mole")(NH_(3))`
`underset("6m mole initially taken")(2NH_(3) + H_(2)SO_(4)) to (NH_(4))_(2).SO_(4)` (1st)
`underset("2m mole reacted")(H_(2)SO_(4) + 2NaOH) to Na_(2)SO_(4) + 2H_(2)O(2 nd)`
Hence m moles of `H_(2)SO_(4)` reacted in 2nd equation = 1.
`rArr` m moles of `NH_(3)` in 1st equation = `2 xx 5 = 10`m moles.
`rArr` m moles of N atom in the organic compound = 10 m moles.
`rArr` mass of `N = 10 xx 10^(-3) xx 14`
= 0.14 g
`rArr % of N = 0.14/1.4 xx 100`
= 10 %