A student weighs 2

A student weighs 2.50 g of KOH and mixes it with 500 g of water. Calculate the concentration of this solution as a percentage, by mass.
-A student weighs 10.0 g of BaCl2 • 2H2O and then adds water until they have 100 g of solution. Calculate the percentage of the Cl- ion in that solution.
-Describe how to prepare 250 ml of a 0.60% KCl solution whose density is 1.14 g / ml starting from 85% KCl.
-In these times, it is useful to have isopropanol, C3H8O 70% by weight available at home, however it is difficult to get it in pharmacies. A student finds a 91% by weight bottle of isopropanol USP with a density of 0.817 g / mL at home. Describe how you would prepare 1.00 L of 70% alcohol by weight in isopropanol. You must include the computations.