I did a search but almost all of the postings were where you have to find pH given acid and base concentration
Here is my scenerio:
Given that your pH of buffer should be 12.2 , where the conjugate acid concentration in the final 100 mL buffer solution should be 0.05 mol/L
You are given KHP, Na3PO4. 12H2O ,0.5 mol/L HCl, 0.5 mol/L NaOH. If only one pair is available as a solid i.e conjugate acid or base , the buffer must be prepared using either 0.5 mol/L HCl or NaOH to get the correct pH(12.2)
I was ask to find:
Concentration of Conjugate base for buffer
Mass of conjugate base and conjugate acid required to prepare the buffer
Volume of NaOH/HCl I need to add to the solid to get the required pH
My steps so Far:
Only one pair is present so since my pH is 12.2 I have to choose a base that closely matches my pH
I choose Na3PO4 12H2O
So I will be adding 0.5 mol/L HCl to it.
pH=pka + log( moles conjuagte base/moles acid)
Con of conjugate acid in 100 mL buffer =0.05 mol/L
therefore 0.05 mol/l * 0.1 L =0.005 mol acid
12.2 =12.15 + log(x/0.005)
moles conjugate base =0.00561 mol
What Do I do Next?