Calculate the pH of a buffer solution prepared by mixing 75 mL of 1.0 M lactic acid  and 25 mL of 1.0 M sodium lactate

Equal volumes of solutions of acids and their sodium salts are mixed to prepare a buffer. The solution with pH closest to 6.0 was prepared by mixing:

For 530.0 mL of a buffer solution that is 0.145 M in HC2H3O2 and 0.130 M in NaC2H3O2, calculate the initial pH and the final pH after adding 0.020 mol of HCl.

How does a buffer solution prevent larger change in pH? What does it mean when a solution has exceeded the buffer capacity?

How many moles of sodium hydroxide would have to be added to 225 mL of a 0.349 M nitrous acid solution, in order to prepare a buffer with a pH of 3.570? moles

A buffer is made by combining 20.0 ml. 0.250 M NHACl with 30.0 mL 0.250 M NH3. A) Calculate the pH of the buffer after 1.00 mL of 6.00 M HCI is added and equilibrium is re-established. B) Calculate the pH of the buffer after 1.00 mL of 6.00 M NaOH is added and equilibrium is re-established. Please help with both parts