Question

5.50g of a certain Compound X, known to be made of carbon, hydrogen and perhaps oxygen, and to have a molecular molar mass of 160./gmol, is burned completely in excess oxygen, and the mass of the products carefully measured:

product	mass
carbon dioxide	9.08g
water	2.48g

Use this information to find the molecular formula of X

.

Answer 1

No. of moles of CO_2 = 9.08/44.01 = 0.2063 moles each mole of CO_2 having carbon = 1 moles So,0.2063 moles of CO_2 having carbon = 0.2603 moles weight of carbon = 0.2063 times 12.01 = 2.478 grams No.of moles of H_2O = 2.48/18.02 = 0.1376 moles each mole of H_2O having hydrogen = 2 times 0.1376 = 0.275 grams Given weight of hydrocarbon = 5.50g Weight of Oxygen = 5.50-(2.478+0.278)= 2.74g No.of moles of oxygen = 2.74/16 = 0.171 moles the mole rastio of C H,O is: C = 1.2 H = 1.6 O = 1 so,empirical formula is = C_1.2H_1.6O_1 multiply by 5 So,the empirical formula is: C_6H_8O_5 so,the molecular formula is equal to empirical formula (since both are having molar mass of 160g/mol) Molecular formula is: C_6H_8O_5

So, the molecular formula is equal to emipirical formuls (since both are having molar mass of 160 g/mol)

Molecular formula is: C6H8O5