294 g of potassium dichromate contains 52 g of chromium and 39 g of potassium. What is the mass percent of oxygen in the compound?

May 21, 2016

Well, clearly it is $\text{Mass of oxygen"/"Mass of potassium dichromate}$ $\times$ 100%.
$\text{%Oxygen by mass}$ $=$ ((294-52-39)*g)/(294*g)xx100% $=$ ??%
I make that about 66%, but don't trust my arithmetic!