What is Dumas Method | Chemistry | Extraclass.com

what is Dumas method Dumas method for nitrogen determination was developed by jean-baptiste Duma during his studies in 1831 even before the gel doll analysis in Dumas method unknown mass of the nitrogen containing organic compound is heated with cupric oxide in an atmosphere of carbon dioxide the carbon and hydrogen in the compound are oxidized to carbon dioxide and water respectively while nitrogen is set free any oxide of nitrogen produced during this process is reduced back to free nitrogen by a heated copper goes the gaseous mixture consisting of co2 h2o and n2 is collected over an aqueous

solution of potassium hydroxide all the gases except nitrogen are absorbed by the solution the volume of nitrogen gas collected is measured from the volume of nitrogen obtained the percentage of nitrogen in the compound is calculated let's say in an experiment the mass of organic compound taken is equal to W grams volume of nitrogen gas collected is equal to V centimeter cube atmospheric pressure is equal to P and M of Hg room temperature is equal to T Kelvin pressure of water vapour at T Kelvin that is a quiz tension is equal to small p mm of

Hg thus pressure of dry nitrogen is equal to P minus P and M of Hg the first step in the estimation process is to calculate the volume of nitrogen gas at STP at experimental conditions volume v1 is equal to measured volume V centimeter cube pressure p1 is equal to atmospheric pressure P minus AK was tension P mm of Hg temperature T 1 is equal to room temperature T Kelvin at STP volume v2 is to be calculated pressure p2 is equal to 760 mm of Hg temperature T 2 is equal to 273 kelvin using the relation

P 1 V 1 by T 1 equal to P 2 V 2 by T 2 we have volume V 2 equal to P minus small P into V into 273 divided by 760 into T now we know that at STP weight of twenty-two thousand four hundred centimeter cube of nitrogen gas is 28 grams therefore weight of V two centimeter cube of nitrogen gas at STP is 28 divided by 22 thousand four hundred into V two grams [Music] amount of nitrogen present in W grams of organic compound is equal to twenty eight divided by twenty two

thousand four hundred into v2 into W now percentage of nitrogen is equal to 28 by twenty two thousand four hundred into v2 into W divided by weight of organic compound in two hundred let's solve an example to estimate the percentage of nitrogen in an unknown compound question zero point thirty gram of an organic compound gave 30 centimeter cube of moist nitrogen gas at 290 Kelvin and 745 mm pressure calculate the percentage of nitrogen using Dumars method give an Aquos tension at 290 Kelvin is equal to 12.7 mm solution we are given a organic compound of

mass equal to zero point thirty grams atmospheric pressure during experiment is equal to given pressure minus act was tension that is p1 equal to seven hundred and forty five minus twelve point seven equal to seven hundred and thirty two point three mm of Hg now let's draw a table to list out the values of variables at experimental and standard conditions in experimental conditions p1 equal to seven hundred and thirty two point three mm of HG t1 equal to two hundred and ninety Kelvin v1 equal to 30 centimeter cube in standard conditions p2 equal to 760

mm of HG t2 equal to 273 Kelvin v2 is unknown now step one is to calculate the volume of nitrogen gas v2 at using the relation P 1 V 1 by T 1 equal to P 2 V 2 by T 2 we get V 2 equal to 27 point 2 centimeter cube step 2 is to calculate the percentage of nitrogen in the organic compound from more concept we know that 22 point four liter or twenty two thousand four hundred centimeter cube of nitrogen gas at STP weighs 28 grams therefore twenty seven point two centimeter cube

of nitrogen gas in the given organic compound weighs 28 into twenty seven point two divided by twenty two thousand four hundred equal to zero point zero three for gram percentage of nitrogen is equal to weight of nitrogen an organic compound divided by weight of organic compound in two hundred that is zero point zero three four divided by zero point thirty in two hundred equal to eleven point three three percent the calculation of percentage of nitrogen present in the organic compound using duma's method is based on simple application of mol concept please like share and comment

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