When a sample of a compound in the vitamin d family was burned in a combustion analysis, 5.983 mg of the compound gave 18.490 mg of co2 and 6.232 mg of h2o. this compound was found to have a molecular mass of 399. what is the molecular formula of this compound? put your answer in form of cxhyoz.

Molecular formula C33H27O3

Explanation:

Given:

Mass of CO2 produced = 18.490 mg

Mass of H2O produced = 6.232 mg

Mass of sample = 5.983 mg

To determine:

Molecular formula of the compound

Calculation:

Step 1: Calculate the mass of carbon in the sample

Molar Mass of CO2 = 44 g/mol

Moles of CO2 =

The carbon content in the sample corresponds to the amount of CO2 produced

Moles of C in the sample = 0.4202

Mass of C = moles * atomic mass of C

                = 0.4202 moles * 12 g/mol = 5.0424 g

Step 2 : Calculate the mass of hydrogen in the sample

Molar Mass of H2O = 18 g/mol

Moles of H2O =

The hydrogen content in the sample corresponds to the amount of H2O produced

Moles of H in the sample = 0.3462

Mass of H = moles * atomic mass of H

                = 0.3462 moles * 1 g/mol = 0.3462 g

Step 3: Mass of O in the sample

Mass of O = Total mass - Mass of C - Mass of H

= 5.983 - 5.0424-0.3462=0.5944 g

Step 4: Moles of O

Moles of O = mass of O/atomic mass = 0.5944/16 = 0.03715

Step 5: Find the empirical formula

Moles of C = 0.4202

Moles of H = 0.3462

Moles of O = 0.03715

Ratio

C =

H =

O =

Empirical formula = C11H9O

Step 6: Find n

Empirical formula mass = 12(11) + 1(9) + 16 = 157

n =

n = 3.0

Step 7: Find molecular formula

(C11H9O)3 = C33H27O3

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