A solution was prepared by dissolving 51 grams of KBr, Potassium Bromide, in 310 ml of water. Calculate the mass percent of potassium bromide in the solution. Alright, so that's going to be mass percent equals the grams of our solute which is KBr divided by grams of solution. Here our solution is made up of our solute KBr and our solvent water. So, we need grams of KBr plus grams of water and this gets multiplied by 100. We already know the grams of KBr so we can immediately plug those in. So, that's 51 grams of KBr here on top and here on the bottom. Now, we need to determine the grams of water, but instead we're given milliliters. Remember that water is roughly about 1 in terms of its density. Water is 1 gram per 1 milliliter. We use that information to help us get the grams of water. Now, this is a piece of information you just have to remember. The density of water is around roughly 1. So that's 310 grams that we have of water. So plug that in and this gets multiplied by 100 and it gives us, at the end, 14.1%. So, this question wasn't that bad, you just had to remember the density of water is 1 and use that to find its grams. Once you find all the components, plug it into the formula to get our final answer.