What mass of K2CrO4 is required to prepare 250cm3 of 0.020 mol dm3 solution? [K2CrO4 = 194.2g mol-1]

The problem is asking for the mass of K2CrO4 needed to make a 0.020 mol dm^-3 solution with a volume of 250 cm^3. To solve the problem, we need to use the formula: mass = moles x molar mass First, we need to calculate the number of moles of K2CrO4 needed. We can do this using the formula: moles = concentration x volume Substituting the given values, we get: moles = 0.020 mol dm^-3 x 0.250 dm^3 moles = 0.005 mol Next, we need to find the molar mass of K2CrO4, which is given as 194.2 g mol^-1. Finally, we can calculate the mass of K2CrO4 needed using the formula: mass = moles x molar mass mass = 0.005 mol x 194.2 g mol^-1 mass = 0.971 g Therefore, the mass of K2CrO4 needed to prepare 250 cm^3 of 0.020 mol dm^-3 solution is 0.97 g. Option A, 0.97g, is the correct answer.