According to the Law of Conservation of Mass, the total mass of the reactants must equal the total mass of the products.
You have:
- 2 grams of potassium (K)
- 5 grams of oxygen (O)
Total mass of reactants = 2 grams (K) + 5 grams (O) = 7 grams.
Therefore, the mass of potassium oxide (K2O) produced will also be 7 grams.
The correct answer is 7 grams.