Hydrochloric acid is used to neutralize the ammonia produced from a Kjeldahl method where all nitrogen organic substances are converted to ammonia. In a 4.37 g sample of organic material, 23.0 mL of 0.280 M HCl (aq) was used up. Determine the mass percentage of nitrogen in the sample.
NH₃(aq) + HCl(aq) → NH₄Cl(aq)

• A. 0.147%
• B. 2.06%
• C. 2.51%
• D. 35.1%

Answer: (B)