Terms in this set (12)
What is a buffer?
A substance that works to prevent a change in pH when acid or base is added
(composed of a weak acid or base and its conjugate salt)
- the composition of a buffer has a pH = pKa
K of H3O+ + OH- <--> 2H2O
How does a buffer work when an acid is added to the solution?
The base present in the buffer will pick up the additional protons donated by the acid to prevent the occurrence of free H+ which will cause a decrease in pH
How does a buffer work when a base is added to the solution?
The acid present in the buffer will donate an H+ to solution to prevent the additional OH- donated by the base from increasing the pH
Strong acid and weak acid mixture
has the pH of a strong acid
Strong base and weak base mixture
has the pH of a strong base
What solutions are used in a titration reaction?
a weak base and strong acid or weak acid and strong base
An equation used to calculate the pH of a buffer solution based on the acids pKa and the log of the [A-]/[HA] ratio
Determining the pH of a buffer solution using the Henderson-Hasselback equation
In a buffer solution- [HA] = [A-], causing the log([A-]/[HA]) --> log(1) = 0
From here, the Henderson-Hasselback equation becomes pH= pKa
In a buffer, with equal concentrations of acid and base, the pH = pKa
If given different acid and base concentrations,
fill them in the ratio and solve for the pH
The concentration of a buffer ([HA]+[A-] = buffer molarity, M)
- how much acid and base is present to react with changes that could cause a pH change
How do you make a buffer solution more resistant to pH change?
Having a higher concentration of acid and base
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