you are given a sample mass of 250g compound that is 45% water. How many grams of water can be recovered from the sample by dehydration?
When I was in school and I got a problem like this I changed up the problem a little to see if I couldn't figure it out. So let's change the problem. We have 250 g sample that is 50% water. How much water is there. We know almost instantly that is 125 g H2O available. How did we get that? You say common sense and that is right BUT mathematically how did we do it.
It's 250 g x 0.50 = 125 g H2O and 125 g of the dehydrated sample left over.
So back to the problem at hand, we do the same thing.
250 x 0.45 = ? = grams H2O.