It was found that compound contained 68.1% carbon, 13.7% hydrogen, and 18.2% oxygen by mass.
a. find empirical formula for the compound.
b. if the molar mass of the compounds is 176.34 g/mol, what it’s the molecular formula?

A. The empirical formula is the simplest ratio of components making up a compound.

In 100 g of the compound

                             C                            H                               O

mass               68.1 g                         13.7 g                         18.2 g

number of moles

                    68.1 g / 12 g/mol        13.7 g / 1 g/mol         18.2 g / 16 g/mol

                     = 5.68 mol                 = 13.7 mol                 1.14 mol

divide by the least number of moles - which is 1.14 mol

                  5.68 / 1.14 = 5.0             13.7 / 1.14 = 12.0     1.14 / 1.14 = 1.0

the ratio of the components C : H : O is 5: 12 : 1

therefore empirical formula is C₅H₁₂O

B. Molecular formula is the actual ratio of the components making up the compound. We need to find the mass of the empirical formula / empirical unit and then find how many empirical units make up the molecular formula

mass of 1 empirical unit - C₅H₁₂O  - 12 g/mol x 5 + 1 g/mol x 12 + 16 g/mol x 1

                                       = 60 + 12 + 16 = 88 g

number of empirical units = molecular formula mass / mass of 1 empirical unit

                                           = 176.34 g/mol  / 88 g = 2.00 = 2

there are 2 empirical formulas in the molecular formula

therefore molecular formula  = 2 x (C₅H₁₂O) = C₁₀H₂₄O₂ ,

therefore molecular formula is C₁₀H₂₄O₂

a graduated cylinder.

explanation: