Could you please help me

Hello there,

Could you please help me answer this question?

What is the empirical formula fir this compound which contains

38.36% Iron
12.33% Carbon
49.32% Oxygen
?????
Apparently if you have a number that has a last number of the decimal or something ending with a 3 or 7, you times it by three, and if you have a 5 you times it by 2?

Could you also please explain the working out because I would like to learn it for other questions? Please do not use complex chemistry words because I will not understand! :)

Many thanks,
10 points for best answer

The easiest way to do these questions is just to use the following table.

element Iron Carbon Oxygen
% 38.36 12.33 49.32 As given in the question
Mr 55.8 12.0 16.0 From periodic table - check these with ur own...
Moles 0.687455 1.0275 3.0825 Moles = mass/ Mr. The % is basically the mass
ratio 1 1.495 4.484 Divide by the smallest number (0.0687455 here)
ratio 2 3 9 Roughly round up to whole numbers, so here, x2.

Sorry, this was formatted to look like a proper table, but then it got undone when I submitted. I hope its still clear. The final answer you would write is: Fe2C3O9 (all the numbers as subscript)

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