Question

0.350 g of an organic compound gave 100 ml of nitrogen collected at 250 K temperature and 700 mm pressure. Calculate the percentage composition of nitrogen in the compound. Use Dumas method.

(a) 25.70%

(b) 35%

(c) 35.71%

(d) 36.88%

This question was addressed to me during an online interview.

Asked question is from Organic Chemistry topic in portion Organic Chemistry – Basic Principles and Technique of Chemistry – Class 11

Answer 1

Right answer is (c) 35.71%

Easy explanation: Here, p = 700 mm; v = 100 ml; t =250 K

Volume of nitrogen at STP = p * v * 273/ 760 * t

                                                = 700 * 100 * 273/ 760 * 250

                                                = 100.57 ml

22,400 ml of nitrogen at STP weighs = 28 g

Then, 100.57 ml of nitrogen weighs = 28 * 100.57/22400

                                                                 = 0.125 g

Therefore, percentage of nitrogen = 0.125 * 100/0.350

                                                          = 35.71%

So, percentage of nitrogen in the organic compound is 35.71%.