Question

The hydrolysis of one mole of sulphate ester produces one mole of protons.In a reaction tube containing 1.0ml of 0.02M TRIS buffer,pH8.08,sulphate ester was incubated with sulphatase for 10 min.At the end of reaction,the pH was reduced to 7.97.Calculated the amount of sulphate ester that has been hydrolyzed in 10 min.give your answer in micromoles of sulphate ester.

Answer 1

I would do something like this. Check my thinking. If the solution is 1 mL x 0.02 M TRIS buffer and the pH is 8.08, that means equal moles TRIS and TRIS*HCl (substitute into the HH equation and base/acid = 1 if you don't see this right away). 1 mL x 0.02 M = 0.02 mmoles buffer or 0.01 mmoles TRIS and 0.01 mmoles TRIS*HCl
...............TRIS + H^+ ==> TRIS*HCl
initial mmoles..0.01...0....0.01 mmole
change...........-x...+x.......+x
final..........0.01-x...+x......0.01+x

Substitute into the HH equation and solve for x.
7.97 = 8.08 + log [(0.01-x)/(0.01+x)]

x will be in mmoles H^+ which will be the same as mmoles of the ester hydrolyzed. You will need to change to micromoles ester hydrolyzed.