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Chemistry Question on Organic Chemistry- Some Basic Principles and Techniques

29.5 mg29.5\, mg of an organic compound containing nitrogen was digested according to Kjeldahl?s method and the evolved ammonia was absorbed in 20 mL20\, mL of 0.1 M HCl0.1\, M\, HCl solution. The excess of the acid required 15 mL15 \,mL of 0.1 M NaOH0.1\, M\, NaOH solution for complete neutralization. The percentage of nitrogen in the compound is

A

59

B

47.4

C

23.7

D

29.5

Answer

23.7

Explanation

Solution

Moles of HCl reacting with ammonia = (moles of HCl absorbed ) - (moles of NaOH solution required) =(20×0.1×10−3)−(15×0.1×10−3)= (20 \times 0.1 \times 10^{-3}) - (15 \times 0.1 \times 10^{-3}) = moles of NH3NH_3 evolved. = moles of nitrogen in organic compound ∴\therefore wt. of nitrogen in org. comp =0.5×10−3×14= 0.5 \times 10^{-3} \times 14 =7×10−3 g= 7\times 10^{-3}\,g %wt=7×10−329.5×10−3=23.7%\% wt = \frac{7\times 10^{-3}}{29.5\times 10^{-3}} = 23.7\%