To calculate the grams of oxygen in 25 moles of sulfur dioxide (SO2), you need to determine the molar mass of oxygen (O) and the number of moles of oxygen present in each mole of SO2.

1. Determine the molar mass of oxygen (O):

- The molar mass of O is approximately 16.00 g/mol.

2. Calculate the moles of oxygen in 1 mole of SO2:

- Each molecule of SO2 contains two oxygen atoms.

3. Calculate the total moles of oxygen in 25 moles of SO2:

- 25 moles SO2 * (2 moles O / 1 mole SO2) = 50 moles O

4. Convert moles of oxygen to grams of oxygen:

- 50 moles O * 16.00 g O / 1 mole O = 800 g O

Therefore, 25 moles of sulfur dioxide contain 800 grams of oxygen.