Question

Isopropyl alcohol is composed of C , H and O combustion of 0.255g of isopropyl alcohol produces 0.561g of co2 and 0.306g of h2o . Determine empirical formula of isopropyl alcohol Cx Hy Oz ? ?

Please I need the answer with explantion ^_^

Answer 1

To calculate the number of g of C, we need to convert g of CO2 to moles. Then moles of CO2 to moles of C. Finally moles of C to grams of C. So, the set up is

Grams of C = (0.561 g CO2)x( 1 mol CO2 / 44.0 g CO2) x (1 mol C / 1 mol CO2) x (12.0 g C / 1 mol C) = 0.153 g C

To calculate the number of g of H, we need to convert g of H2O to moles. Then moles of H2O to moles of H. Finally moles of H to grams of H. So, the set up is

Grams of H =(0.306 g of H2O)x(1 mol H2O / 18.0 g H2O)x(2 mol H / 1 mol H2O)x(1.01 g H / 1 mol H) = 0.0343 g H

The total mass of the sample is 0.255 g. It is nothing but sum of C, H, O.

So, mass of O = Total mass - (Mass of C + Mass of H)

= 0.255 -(0.153 + 0.0343)

= 0.068 g of O

Now, we need to find moles of each.

Moles of C = 0.153 g / 12.0 g/mol = 0.0128 mol

Moles of H = 0.0343 g / 1.01 g/mol = 0.0340 mol

Moles of O = 0.068 g / 16.0 g/mol = 0.0043 mol

Now, the next step is to find the mole ratio. The relative number of moles of each element is found by dividing each number by the smallest number, 0.0043.

Thus, the mole ratio of C;H:O = 2.98 : 7.91 : 1.00

C : H: O = 3 : 8: 1

Thus, the empirical formula is C3H8O