Saltpeter is a compound made of potassium (k), nitrogen (n), and oxygen (o). every 100.00 g of saltpeter contains 38.67 g potassium and 13.86 g nitrogen. what is the mass of oxygen contained in 328.0 mg of saltpeter

First, we need to compute the mass of oxygen found in 100 grams of saltpeter:
mass of oxygen = 100 - (mass of potassium + mass of nitrogen)
                          = 100 - (38.67 + 13.86)
                          = 100 - 52.53
mass of oxygen in 100 grams saltpeter = 47.47 grams

Now, we can use cross multiplication to find the mass of oxygen in 328 grams saltpeter as follows:
mass of oxygen = (328 x 47.47) / 100 = 155.7016 grams

The answer is 65.3312