Composition Stoichiometry

Question

How can I find the mass of each element that is present in ! mole of the compound of C2H6 ?

Answer 1

I'll assume you meant 1 mole of C₂H₆

1 mole of C₂H₆ contains 2 moles of C and 6 moles of H.

2 moles of C has a mass of 2 x 12.011 = 24.022 g of C

6 moles of H has a mass of 6 x 1.0079 = 6.0474 g of H

Answer 2

Assuming you don't know the number of moles ( you wrote ! moles):

C₂H₆ is ethylene and has a molecular weight of 2 *12 g/mole + 6 * 1 g/mole = 30 g/mole

Fraction by mass of H: 6 * 1 g/mole / 30 g/mole = 0.20

Fraction by mass of C: 2 * 12 g/mole / 30 g/mole = 0.80

In ! moles of C₂H₆

there are (0.20 g H / 1.00 g C₂H₆)*(30 g C₂H₆ / mole C₂H₆)*( ! moles C₂H₆) = 6.0 * ( ! ) g of H

and (0.80 g C / 1.00 g C₂H₆)*(30 g C₂H₆ / mole C₂H₆)*( ! moles C₂H₆) = 24.0 * ( ! ) g of C