Question
29.5 mg of an organic compound containing nitrogen was digested according to Kjeldahl’s method and the evolved ammonia was absorbed in 20 mL of 0.1 M HCl solution. The excess of the acid required 15 mL of 0.1 M NaOH solution for complete neutralization. The percentage of nitrogen in the compound is
-
59.0
-
47.4
-
23.7
-
29.5
Solution
C.
23.7
m moles of HCl = 20 × 0.1 = 2
m moles of NaOH = 15 × 0.1 = 1.5
∴ m moles of HCl that consumed NH3 = 0.5
m moles of NH3 = 0.5
milligrams of N in NH3 = 0.5 × 14 = 7 mg
