Which of the following combinations would make a buffer with the greatest buffering capacity? Here we're dealing with one liter of solution. If we take a look in options A to D, we have different mole amounts of weak acid and conjugate base for both A&B. We're dealing with chlorous acid, which is a weak acid and we're dealing with sodium chloride, it's conjugate base for C&D. We're dealing with nitrous acid and potassium nitrite.
If we take a look here, if we compare A&B to one another, we have 0.25 moles versus 0.35 moles for our weak acids, 0.20 moles of our conjugate base, 0.25 moles of our conjugate base. B has higher values for weak acid and conjugate base, so it have a greater buffering capacity, so B would be better than A.
If we look at C, C also has weak acid and conjugate base and the mole amounts are even larger. So option C will be better than option B. And then finally, if we're comparing C&D, we have 35 moles versus 50 moles, 30 moles versus 48 moles. Option D will be the better answer since our weak acid and conjugate base have higher values, therefore giving them the greater buffering capacity.
So here our final answer for this question will be option D.
