A compound of carbon,hydrogen and nitrogen contains these elements in the ratio 9 : 1 : 3.5.If its molecular mass is 108,what is the molecular formula?

Given, the ratio of carbon, hydrogen and nitrogen in the compound is 9 : 1 : 3.5.

Therefore, in 100 g of compound,

Mass of carbon = 9 g

Mass of hydrogen = 1 g

Mass of nitrogen = 3.5 g

Moles of carbon = 9/12  = 0.75

Moles of hydrogen = 1/1 = 1

Moles of nitrogen = 3.5/14 = 0.25

Ratio of moles of carbon, hydrogen and nitrogen = 0.75 : 1 : 0.25

 = 3 : 4 : 1

Empirical formula of the compound = C3H4N

Empirical formula mass = 12 x 3 + 4 x 1 + 14 x 1

 = 54 u

Molecular mass = 108 u

 n = 108/54

    = 2

Therefore, molecular formula = (empirical formula) 2

 =  (C3H4N)2

 = C6H8N2

 

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