A 18.2 g sample of an unknown compound contains 0.7 g of oxygen. What is the percent by mass of oxygen in the compound?

Look at your post under the screen name lea. Bob Pursley worked that problem for you.

To find the percent by mass of oxygen in the compound, you need to divide the mass of oxygen by the total mass of the compound and then multiply by 100 to express it as a percentage.

Step 1: Calculate the percent by mass of oxygen:
Mass of oxygen = 0.7 g
Total mass of the compound = 18.2 g

Step 2: Divide the mass of oxygen by the total mass of the compound:
Percent by mass = (Mass of oxygen / Total mass of the compound) × 100

Percent by mass = (0.7 g / 18.2 g) × 100

Step 3: Calculate the value:
Percent by mass = 3.846 × 100

So, the percent by mass of oxygen in the compound is approximately 3.846%.