Empirical formula from MPC

AhYeon_Kwon_2H
Posts: 48
Joined: Fri Sep 28, 2018 12:27 am

Empirical formula from MPC

When we're determining the empirical formula from the mass percentage composition, would the molar ratio be the the ratio found when we divide all the moles by the smallest mole, or the ratio with the whole numbers? Or does it even matter?

Ex: Is molar ratio 1.00 : 1.33 : 1.00 or 3 : 4 : 3?

Thank you! :)

Lauren Huang 1H
Posts: 60
Joined: Fri Sep 28, 2018 12:16 am

Re: Empirical formula from MPC

There are no decimals used in empirical formulas so you would have to divide the moles by the smallest number of moles calculated and round to the nearest whole number. So in this problem, you would use the molar ratio 3 : 4 : 3

Moryel Yashar 1J
Posts: 31
Joined: Fri Sep 28, 2018 12:15 am

Re: Empirical formula from MPC

Molecules must have whole atoms, so anytime the values we obtain after dividing the moles by the smallest number of moles aren't whole or at least near whole numbers, we must multiply the values by a number that would result in whole numbers.

For the example you have provided, we would need to multiply the values 1.00, 1.33, and 1.00 by 3 to obtain a molecular ratio of 3:4:3.

Sona Hakobyan 3J
Posts: 45
Joined: Fri Sep 28, 2018 12:25 am

Re: Empirical formula from MPC

Empirical Formulas requires the simplest whole number ratio in a compound, therefore it would be 3:4:3.