How can I prepare a 0.1M NaOAc buffer at pH 5 using titration?

In summary, to create a pH 5 buffer using acetic acid, you would need a 0.2M solution, titrate it to pH 5, and make sure to record how much sodium acetate was used.
  • #1
ReidMerrill
66
2
For a lab I need to create a 0.1M solution of NaOAc buffer at pH 5
It's been a while since I worked with buffers. I'm struggling to find a way to get both the proper morality and proper pH.
My first though was to create a 0.2M solution of acetic acid and titrate it to pH 5 using sodium hydroxide. The problem is when I tried to calculate the pH of 0.2M solution of acetic acid I got a pH higher than 5 so I couldn't use sodium hydroxide to adjust the pH. I think this was a calculation error on my part though.

Any help would be greatly appreciated.
 
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  • #3
Borek said:
Check this out: http://www.chembuddy.com/?left=buffers&right=toc

Yes, your calculation of pH is faulty, as pH of 0.2 M acetic acid is below 3.
I did some Google snooping and apparently the pH of a 0.1M solution of acetic acid is 2.88.

In that case, how do I raise the pH without lowering the molarity?
 
  • #4
There are worked out examples at the link provided, why don't you check them?
 
  • #5
ReidMerrill said:
For a lab I need to create a 0.1M solution of NaOAc buffer at pH 5
It's been a while since I worked with buffers. I'm struggling to find a way to get both the proper morality and proper pH.
My first though was to create a 0.2M solution of acetic acid and titrate it to pH 5 using sodium hydroxide. The problem is when I tried to calculate the pH of 0.2M solution of acetic acid I got a pH higher than 5 so I couldn't use sodium hydroxide to adjust the pH. I think this was a calculation error on my part though.

Any help would be greatly appreciated.
You COULD actually do the titration to determine, ultimately how to prepare your pH 5 buffer, as long as you carefully record how much of what concentrations of the solutions you used, as as long as you properly calibrated your pH meter before doing the titration. You should be able to figure how much sodium acetate is present once you reached pH 5. (This should be a beginner's lab exercise.)
 

1. What is the purpose of a buffer solution?

A buffer solution is used to maintain a stable pH level in a solution by resisting changes in pH when small amounts of acid or base are added. It helps to keep the solution at a specific pH, which is important for many chemical reactions and biological processes.

2. How is the pH of a buffer solution determined?

The pH of a buffer solution is determined by the concentration of the weak acid and its conjugate base. The ratio of these two components, known as the acid dissociation constant (Ka), determines the pH of the solution.

3. What is the relationship between pH and molarity in a buffer solution?

In a buffer solution, the pH and molarity are directly related. The higher the concentration of the weak acid and its conjugate base, the more effective the buffer will be at maintaining a stable pH.

4. How does temperature affect the pH and molarity of a buffer solution?

The pH and molarity of a buffer solution can be affected by changes in temperature. Generally, an increase in temperature will decrease the effectiveness of a buffer solution, while a decrease in temperature will increase its effectiveness.

5. Can a buffer solution have a pH of 7?

Yes, a buffer solution can have a pH of 7. This means that the concentration of the weak acid and its conjugate base are equal, resulting in a neutral pH. However, a buffer solution is most commonly used to maintain a specific pH range, rather than a specific pH value.

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