Question

The empirical formula of a molecule is C2H6. In an experiment, the Molar mass of the molecule was determined to be 90.21g/mol. Use this information to determine the molecular formula of the molecule.

Answer 1

Answer:

C₆H₁₈

Explanation:

Let's say x is the subscript of carbon and y is the subscript of hydrogen.  We know from the empirical formula that the ratio of x to y is 2 to 6.

x / y = 2 / 6

We also know from the molar mass that:

12.01x + 1.01y = 90.21

Solving the system of equations:

2y = 6x

y = 3x

12.01x + 1.01(3x) = 90.21

12.01x + 3.03x = 90.21

15.04x = 90.21

x = 6

y = 3x

y = 18

The molecular formula is therefore C₆H₁₈.