Problem: Consider a buffer composed of the weak acid HA and its conjugate base A–. Which pair of concentrations results in the most effective buffer?a) 0.10 M HA; 0.10 M A–b) 0.50 M HA; 0.50 M A–c) 0.90 M HA; 0.10 M A–d) 0.10 M HA; 0.90 M A–

FREE Expert Solution

We’re being asked to determine which of the given solutions is the most effective buffer.


Recall that a buffer can be composed of the following:

weak base and its conjugate acid
weak acid and its conjugate base
weak acid and a strong base 

▪ concentration of weak acid > concentration of strong base

weak base and a strong acid 

concentration of weak base > concentration of strong acid


The maximum buffering capacity of a solution is when the pH of the solution is equal to pKa and the buffer range of a solution is pH = pKa ± 1

 maximum buffering capacity:              pH = pKa

 buffering range:              pH = pKa ± 1


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Problem Details

Consider a buffer composed of the weak acid HA and its conjugate base A. Which pair of concentrations results in the most effective buffer?
a) 0.10 M HA; 0.10 M A
b) 0.50 M HA; 0.50 M A
c) 0.90 M HA; 0.10 M A
d) 0.10 M HA; 0.90 M A

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