Amount (in moles) = Molarity × Volume Amount (in moles) = 0.20 mol/dm³ × 100.0 cm³ / 1000 cm³/dm³ = 0.020 moles Now, we can calculate the mass using the formula: Mass = Amount × Molar Mass Mass = 0.020 moles × 40.0 g/mol = 0.80 g So, the correct answer is:0.80 g