What mass of potassium oxide was used if some potassium oxide was placed in 9g of water and 112g of potassium hydroxide was produced?

The answer to this is 103 grams of potassium oxide. There are a lot of people who may know that this is the answer because they have seen this question before but they have no idea how this was solved. The word equation for this is Potassium oxide + water = potassium hydroxide.

Based on that, the numerical equation is going to be __ + 9g = 112g. Since you are going to apply the law of conversation of mass, you will change the + to a - sign. This is because you are solving for the missing mass. You can subtract 112g and 9g and what will you get? You will get 103g. This is the reason why this is the answer.