How many grams of KOH are required to prepare 400 mL of a 0.350 M KOH solution?

• A. 9.80 g
• B. 7.84 g
• C. 4.20 g
• D. 5.60 g

Answer: (B)

Verified step by step guidance

1. Identify the given information: volume of solution (400 mL) and molarity (0.350 M). Convert the volume from milliliters to liters by dividing by 1000, since molarity is expressed in moles per liter.
2. Use the molarity definition formula to find the number of moles of KOH needed: \(\text{moles} = M \times V\), where \(M\) is molarity and \(V\) is volume in liters.
3. Calculate the molar mass of KOH by adding the atomic masses of potassium (K), oxygen (O), and hydrogen (H). This will give you grams per mole.
4. Convert moles of KOH to grams using the formula: \(\text{mass (g)} = \text{moles} \times \text{molar mass (g/mol)}\).
5. The result from the previous step will give you the grams of KOH required to prepare 400 mL of a 0.350 M solution.