[aemalcolm]

So we've moved onto buffers and I'm struggling again....
Any suggestions would be very helpful, for example
A buffer contains 0.01 mol of lactic acid (pKa = 3.86) and 0.05 mol of sodium lactate per liter
*Calculate pH of the buffer - which I was able to do using pH = pKa + log (A-/HA)
pH = 4.6 but here's where I struggle
*Calculate the change in pH when 5 mL of 0.5 M HCl is added to 1 L of the buffer....? Any suggestions?

[Yggdrasil]

How do you think HCl will react with the solution?  Will it affect the amount of lactic acid?  Will it affect the amount of sodium lactate?