Solution (b) has the greater buffer capacity.
Work Step by Step
The solution with the higher quantity of moles of its acid and its buffer has the greater buffer capacity. Since both solution have the same volume, the concentration will determine the number of moles. (a) 0.20M of its acid, 0.30M of its base. (b) 0.40M of its acid, 0.60M of its base. Therefore, the buffer with the greater capacity is the second one (b).