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