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?

The answer is 69.048%.

Mass of potassium dichromate (K₂Cr₂O₇) is 294 g, which is a 100%.

Given mass of chromium is 52 g. So, the mass percent of chromium in the compound is 17.687%:

52 g : x% = 294 g : 100%

x = 52 : 294 * 100 %

x = 17.687%

Given mass of potassium is 39 g. So, the mass percent of potassium in the compound is 13.265%:

39 g : x% = 294 g : 100%

x = 39 : 294 * 100 %

x = 13.265%

Therefore, the mass percent of oxygen in the compound is 69.048%:

100% - 17.687% - 13.265% = 69.048%.