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Stoichiometry question! Help, please

Q- on heating, 0.02 mol of the element M reacts with 0.025 mol of Oxygen gas. What is the empirical formula of the Oxide of M?
I tried doing this question, but I keep getting a wrong answer! :dontknow:

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What empirical formula do you get?

The numbers in the empirical formula are the lowest whole number mole ratios.
You have a mole ratio of 0.02 : 0.025 but it isn't a whole number ratio so you need to divide them both by the smallest number to get a 1: something ratio and then multiply them until they are both whole numbers and put those into the empirical formula.
(edited 9 years ago)
Reply 2
Original post by Madasahatter
You have a mole ratio of 0.02 : 0.025


Actually - no, that's not the mole ratio you have.

What do you know about oxygen?
Original post by Borek
Actually - no, that's not the mole ratio you have.

What do you know about oxygen?


Oops! Read the question! :colondollar:
Reply 4
Original post by Madasahatter
What empirical formula do you get?

The numbers in the empirical formula are the lowest whole number mole ratios.
You have a mole ratio of 0.02 : 0.025 but it isn't a whole number ratio so you need to divide them both by the smallest number to get a 1: something ratio and then multiply them until they are both whole numbers and put those into the empirical formula.


Thanks for answering, I discussed the question with my chemistry teacher today, so I'm good :smile: We need to multiply the 0.025 by 2, because Oxygen gas is always in molecules, but we need to use atoms for the empirical formula.
*Then* we do the dividing by the smaller number (0.02). The ratio is then 1 : 2.5.
It's a multiple choice question (sorry,I forgot to mention that earlier! :s-smilie:) And the answer is M2O5.

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