An organic compound contains only carbon, hydrogen and oxygen. A sample of this

Question

An organic compound contains only carbon, hydrogen and oxygen. A sample of this compound, Weighing 450.40 g, is found to contain 225.21 g of carbon and 25.20 g of hydrogen. The empirical formula of this compound is: CH_2O C_2H_2O C_2H_3O_2 C_2H_4O_3 C_3H_2O_4 C_3H_4O_2 C_3H_3O_2 C_4H_3O_2 At elevated temperatures, copper (Cu) reacts with sulfur (S) to form cuprous sulfide, Cu_2S. When a quantity of 100.0 g of copper is heated with 50.0 g of sulfur, the amount of cuprous sulfide formed is: 62.61 g 125.23 g 159.15 g

Explanation / Answer

Given the total mass of the organic compound = 450.40 g

mass of C in the compound = 225.21 g

Atomic mass of C = 12.0 g/mol

Hence moles of C in the compound = mass / atomic mass = 225.21 g / 12.0 g/mol = 18.7675 mol C

mass of H in the compound = 25.20 g

Atomic mass of H = 1.0 g/mol

Hence moles of H in the compound = mass / atomic mass = 25.20 g / 1.0 g/mol = 25.20 mol H

mass of O in the compound = 450.40 g - 225.21 g - 25.20 g = 199.99 g

Atomic mass of O = 16.0 g/mol

Hence moles of O in the compound = mass / atomic mass = 199.99 g / 16.0 g/mol = 12.50 mol O

Now the molar ratio of C, H and O in the compound

= moles of C : moles of H : moles of O

= 18.7675 mol C : 25.20 mol H : 12.50 mol O

Dividing the above molar ratio by the smallest number 12.50 we get

= 18.7675 mol C / 12.50 : 25.20 mol H / 12.50 : 12.50 mol O / 12.50

= 1.5 mol C : 2.0 mol H : 1.0 mol O

In order to round off the above ratio, we need to multiply the ratio by 2

= 3.0 mol C : 4.0 mol H : 2.0 mol O

Hence empirical formulae of the compound is

C3H4O2 (answer)

Hence option (f) is correct.

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