Question: what is the mass percent of water in bacl2h2o?
Answer: Barium chloride dihydrate has a molar mass of 244.26 g mol−1 , which means that one mole of hydrate has a mass of 244.26 g . Since one mole of hydrate contains 2 moles of water, and since water has a molar mass of 18.015 g mol−1 , it follows that you get 2×18.015 g of water for every 244.26 g of hydrate.