12.33. A sample of 0.50 g of an organic compound was treated according to Kjeldahl’s method. The ammonia evolved was absorbed in 50 ml of 0.5M H₂SO₄. The residual acid required 60 ml of 0.5 M solution of NaOH for neutralization. Find the percentage composition of nitrogen in the compound.

<p>Step I: Calculation of volume of unused acid i.e. V2 =? </p><p>V1 = Volume of NAOH solution required = 60 cm³&nbsp;</p><p>N1 = Normality of NaOH solution = ½ N</p><p>N2 = Normality of H₂SO₄= 1N</p><p>Applying N1V1 = N2V2</p><p>½ N x 60 cm³&nbsp;= 1N x V2</p><p>Or V2 = 30 cm³</p><p>Step II: calculation of volume of acid used</p><p>Volume of acid added = 50 cm³</p><p>Volume of unused acid = 30 cm³</p><p>Volume of acid used = 50 – 30 = 20 cm³</p><p>Step III: Calculation of % of nitrogen</p><p>Mass of compound = 0.50 g</p><p>Volume of acid used = 20 cm³</p><p>Normality of acid used = 1 N</p><p>% of nitrogen = (1.4 x 20 x 1) / 0.50 = 56%</p>

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