To calculate the amount of CuSO4 needed, you can use the formula: moles = molarity x volume. In this case, we want 75ml of a 0.25M solution, so the calculation would be: (0.25 mol/L) x (0.075 L) = 0.01875 moles of CuSO4.
To convert moles to grams, you need to know the molar mass of CuSO4, which is 159.609 g/mol. Multiply the number of moles by the molar mass to get the mass in grams. In this case, 0.01875 moles of CuSO4 would be equal to 2.99 grams (0.01875 mol x 159.609 g/mol = 2.99 g).
To prepare a 0.25M solution using solid CuSO4, you will need to weigh out 2.99 grams of CuSO4 (calculated in question 2) and add it to a volumetric flask. Then, add enough water to make a total volume of 75ml. Make sure to mix the solution well to ensure all of the solid is dissolved.
Ideally, you should use deionized or distilled water to prepare the solution. This is because tap water may contain impurities that could affect the accuracy of the solution. However, if deionized or distilled water is not available, you can use tap water, but make sure to filter it first to remove any impurities.
To check the accuracy of the prepared solution, you can use a spectrophotometer or a titration method. These methods will allow you to measure the concentration of the solution and compare it to the desired concentration of 0.25M. Adjustments can be made if necessary by adding more solid or water to the solution.