According to the Law of Conservation of Mass, the total mass of the reactants equals the total mass of the products.
In this reaction, you're starting with:
- 2 grams of potassium (K)
- 5 grams of oxygen (O)
To find the total mass of the reactants, you add the mass of potassium and oxygen: \[ 2 \text{ grams (K)} + 5 \text{ grams (O)} = 7 \text{ grams (total reactants)} \]
Thus, according to the Law of Conservation of Mass, the mass of potassium oxide (K2O) produced will also be 7 grams.
Therefore, the answer is: 7 grams