Question

A compound is found to consist of 63% manganese and 37% oxygen by mass. What is the empirical formula?

Answer 1

`MnO_2`
Procedure:
% per 100wt => gms per 100 wt => moles => mole ratio => normalize (divide by smaller mole value) => adjust fraction* => Empirical Ratio => Empirical Formula

Explanation:

%Mn = 63% => 63gms = 63g/(55g/mole) = 1.15 mole Mn
%Oxy = 37% => 37gms = 37g/(16g/mole) = 2.31 mole Oxy

Mn:Oxy => `(1.15:2.31)` => `(1.15)/(1.15)`:`(2.31)/(1.15)` => 1:2 Empirical Ratio

=> Empirical Formula => `MnO_2`

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* If normalized ratio is in fractions of 0.25 or 0.75 adjust by multiplying by 4, or if fraction is 0.50, multiply by 2 => smallest whole number ratio => Empirical Ratio => Empirical Formula.