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FeDeX_LaTeX
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Homework Statement
A student sets out to make a buffer solution. The student measures out 27 cm3 of 0.050 mol dm-3 HA solution and reacts with one-third of the volume of 0.10 mol dm-3 sodium hydroxide needed for complete neutralisation.
(i) Calculate the volume of sodium hydroxide that the student uses.
(ii) Calculate the pH of the resulting buffer solution, given that Ka = 9.3 x 10-4.
Homework Equations
n = cV
HA <--> H+ + A- (<--> indicating a dynamic equilibrium)
The Attempt at a Solution
For (i) I'm getting 4.5 cm3 which is in agreement with the mark scheme.
For (ii) the answer is 2.73, but I am not getting that, I'm getting 3.33.
Their answer implies that [A-]/[HA] = 0.5, but how are they getting this?