Question

The Kjeldahl method was used to determine the nitrogen content of a protein. A 275 uL aliquot of a 45.1 mg/mL protein solution was digested in boiling sulfuric acid. The solution was made basic and the liberated NH, was collected in 5.00 mL of 0.0512 M HCl. A volume of 7.01 mL of 0.0174 M NaOH was required to react with the excess HCl. Calculate the weight percent of nitrogen in the protein. weight percent: wt%N

Answer 1

The objective is to calculate the weight percent of nitrogen in the protein to the following data. ANS Given that) IL Moles of Hel=0.0512 MX 5.0mL X on. C1000 ml. = 0.000256 mol IL Moles of NaOH = 0.0174Mx7.01 mL X- 1000 ml. = 0.000122mol. Moles of NH3 s Total moles of HCl- moles of Naoh -0.000256 mol-0.000122 mol = 0.000134 moli - Imol N Mass of nitrogen = 0.000134 mol NHq x Imolnita 14.09 N IMOLN = 0.00198

Mass x of a 225 w protein = 275 uLa protein 45. lng ime of . Iml 1000 ML X- ig ^ 1000mg =0.01249 0.0019 9 x100 0.01249 Mass percentage of nitrogen = = 0.153 x 100 = 15.3 wt% N - o