Question

1.50 g of a certain Compound X, known to be made of carbon, hydrogen and perhaps oxygen, and to have a molecular molar mass of 44. g/mol, is burned completely in excess oxygen, and the mass of the products carefully measured: product carbon dioxide mass 4.50 g water 2.46 g Use this information to find the molecular formula of X Janation Check

Answer 1

Let molecular formula of compound X = CxHyOz

CxHyOz + 1/2 (2x + y/2 - 2z) O2 -------------------> xCO2 + y/2H2O ....... (A)

m.w. of compound "X" = 44

12x + y + 16z = 44 ..................................(1)

from the equation A

44 g Organic compund produces = 44x g CO2

.: 1.5 g Org. Comp. will produce  

= 4 x 1.59002

4.5 g = 1.5 x

x = 3

Similarly for water

4 g Organic compund produces = y/2 g H2O

1.5 g Org. Comp. will produce = 9y * 1.5 / 44 g H2O

2.46 = 9 * 1.5y / 44

y = 8

on putting the value of x and y in equation (1)

12 x 3 + 8 + 16z = 44

z = 0

hence in compound X oxygen is not present.

Answer :

Molecular formula of compound X = C3H8