Answer:
15 g
Explanation:
1. According to the Law of Conservation of Mass, the sum of the products should be 105 g because 70 g + 35 g = 105 g.
2. If 90g of solution was produced and there's supposed to be 105 g, then the remaining grams would be equal to the mass of the gas.
3. 105 g - 90g = 15 g
