To answer this, we need to find the molar mass of nickel in nickel (II) fluoride. The formula for nickel (II) fluoride is NiF2. This gives us the molar mass of 96.69 g. The mass percentage of nickel is 60.70% approximately (as we divide the molar mass of nickel by that of nickel (II) fluoride), and 60% of 25g gives us 15.17 g