How many grams of CuSO_4·5H_2O are required to prepare 25 mL of a 0.020 M stock solution?

• A. 0.250 g
• B. 0.125 g
• C. 0.500 g
• D. 0.050 g

Answer: (B)

Verified step by step guidance

1. Identify the given information: volume of solution (V) = 25 mL, molarity (M) = 0.020 M, and the solute is copper(II) sulfate pentahydrate (CuSO_4\cdot5H_2O).
2. Convert the volume from milliliters to liters because molarity is in moles per liter: \(V (L) = \frac{25}{1000}\).
3. Calculate the number of moles of CuSO_4\cdot5H_2O needed using the molarity formula: \(n = M \times V\), where \(n\) is moles, \(M\) is molarity, and \(V\) is volume in liters.
4. Determine the molar mass of CuSO_4\cdot5H_2O by summing the atomic masses of all atoms in the formula: Cu, S, 4 O, and 5 H_2O molecules.
5. Calculate the mass of CuSO_4\cdot5H_2O required using the formula: \(\text{mass} = n \times \text{molar mass}\). This will give the grams needed to prepare the solution.