The mass of potassium hydroxide required to make 300.ocm3 of 0.4 moldm-3 solution is {KOH = 56.0}

To calculate the mass of potassium hydroxide required, we can use the formula: mass = moles × molar mass First, let's calculate the number of moles of potassium hydroxide required to make 300 cm³ of 0.4 mol dm^-3 solution: moles = concentration × volume moles = 0.4 mol dm^-3 × 0.3 dm³ = 0.12 moles The molar mass of potassium hydroxide (KOH) is 56.0 g mol^-1, so we can now calculate the mass of KOH required: mass = moles × molar mass mass = 0.12 moles × 56.0 g mol^-1 = 6.72 g Therefore, the mass of potassium hydroxide required to make 300 cm³ of 0.4 mol dm^-3 solution is 6.72 g. So, the correct option is (C) 6.72g.