Final answer:
Options (a), (c), (d), and (e) exceed the buffer capacity of the solution because the moles of added HCl or NaOH are greater than the moles of buffer components present in the solution.
Step-by-step explanation:
The question is about determining which additions to a buffer solution would exceed its buffer capacity. A buffer solution of 250.0 mL contains 0.20 M HA and 0.10 M A-. We consider additions of strong acid (HCl) and strong base (NaOH) in various amounts and concentrations.
- a) Adding 30ml of 1M NaOH results in 0.03 mol NaOH, which is more than the amount of acid HA available to react with (0.20 M * 0.250 L = 0.05 mol). This will exceed the buffer capacity.
- b) Adding 20ml of 1M HCl results in 0.02 mol HCl, exactly the amount of base A- available, so it would not exceed the buffer capacity.
- c) Adding 30ml of 1M HCl results in 0.03 mol HCl, which is more than the buffer can neutralize, thus exceeding the buffer capacity.
- d) Adding 20ml of 3M HCl results in 0.06 mol HCl, which exceeds the buffer capacity.
- e) Adding 20ml of 3M NaOH results in 0.06 mol NaOH, which also exceeds the buffer capacity.
Therefore, options (a), (c), (d), and (e) exceed the buffer capacity, as the number of moles of added HCl or NaOH surpasses the moles of buffer components present in the buffer solution.