In 175 ml of water, 25 g of CuSO4 * 5H2O was dissolved. Calculate the mass fraction of the anhydrous salt in the solution.

mass fraction = mass of substance \ mass of solution
mass of water = density * volume = 175 * 1 = 175 g
our solution consists of water and salt, i.e. the mass of the solution is 175 + 25 = 200 g
if 25 g is 250 g / mol (molar mass of all salt), then 160 g / mol (molar mass of anhydrous salt) accounts for 16 g (in proportion, 25 * 160: 250)
mass fraction of anhydrous salt = 16: 200 * 100% = 8%