Answer:
Step-by-step explanation:
1. Word equation:
- mercury(II) oxide → mercury + oxygen
2. Balanced molecular equation:
3. Mole ratio
Write the ratio of the coefficients of the substances that are object of the problem:

4. Calculate the number of moles of O₂(g)
Use the equation for ideal gases:

5. Calculate the number of moles of HgO

6. Convert to mass
- mass = # moles × molar mass
- molar mass of HgO: 216.591g/mol
- mass = 0.315mol × 216.591g/mol = 68.3g