Posted: Jan 30, 2016 2:51 pm
No probs.
Couple of things come to mind - I did wonder if the way you stated the problem made it harder than it needed to be.
Rather than A/B, B/C and C/D, it's really B/A, C/B, D/C that are the respective [base]/[acid] values, where A, B, C, D refer to the sequentially deprotonated forms.
It's a small point, but it's more obvious what you have to multiply by each time if you get the fractions the right way up and referring to the right species.
If you're helping a younger student with this stuff, might be an idea to make sure that (s)he knows how to calculate the pKa values from the information given too.
Couple of things come to mind - I did wonder if the way you stated the problem made it harder than it needed to be.
Rather than A/B, B/C and C/D, it's really B/A, C/B, D/C that are the respective [base]/[acid] values, where A, B, C, D refer to the sequentially deprotonated forms.
It's a small point, but it's more obvious what you have to multiply by each time if you get the fractions the right way up and referring to the right species.
If you're helping a younger student with this stuff, might be an idea to make sure that (s)he knows how to calculate the pKa values from the information given too.