Should cadmium sulfate affect the pH of my buffer?

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In summary: CdCl2 will cause pH decrease, NaAcetate will cause pH increase.The reaction between cadmium cation and acetate is what is responsible for the pH change.
  • #1
philip041
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I have a 0.2M solution of Sodium Acetate, (which surprisingly seems to be at pH7.8, (we calculated it should be around pH9)). We then add Cadmium Sulfate, and adjust the pH using acetic acid to pH5. However, when I add the Cadmium Sulfate the pH drops.

Surely this can't happen?
 
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  • #2
Are you adding solid sulfate, or solution? If solution - what is its pH?

Cations of many metals are able to lower pH of the solution reacting with water.
 
  • #3
Solid Cadmium Sulfate
 
  • #4
How come a metal can affect pH if pH is a measure ph hydrogen ions?
 
  • #5
See my previous answer. Hydrolyzis.
 
  • #6
philip041 said:
I have a 0.2M solution of Sodium Acetate, (which surprisingly seems to be at pH7.8, (we calculated it should be around pH9)). We then add Cadmium Sulfate, and adjust the pH using acetic acid to pH5. However, when I add the Cadmium Sulfate the pH drops.

Surely this can't happen?

[tex]Cd^{++}\ +\ H_2O\ \rightarrow\ CdOH^+\ +\ H^+\ \ \ pKa\ =\ 7.6[/tex]

So with Cadmium the reduction of pH is slight. Try to do the same with Hg++ or Fe+++.
 
  • #7
lightarrow said:
[tex]Cd^{++}\ +\ H_2O\ \rightarrow\ CdOH^+\ +\ H^+\ \ \ pKa\ =\ 7.6[/tex]

So with Cadmium the reduction of pH is slight. Try to do the same with Hg++ or Fe+++.

I love you
 
  • #8
You would love yourself, you just ignored what I have posted earlier. This is metal cation reacting with water, lowering pH. This reaction is called hydrolysis. It is all in this thread.
 
  • #9
Yes, I read your post. I also read about hydrolysis. I also understand it. I also have a sense of humour. Get a grip.
 
  • #10
HA! I just saw you have an award for humour!
 
  • #11
The target is becoming lost here. Cadmium would be reacting with something, not necessarily water, affecting the pH.
 
  • #12
Cadminum will also get complexed by acetate, up to four ligands per cation. Looks like in solution that is 0.1M in both Cd and acetate about 40% of cadmium will be complexed. However, concentration of undissociated acetic acid goes up (even if concentration of acetate anion goes down; one may expect that will shift dissociation right), so it must be cadmium hydrolysis that is responsible for the pH change.

0.1M CdCl2 and 0.1M NaAcetate.
 

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1. Does cadmium sulfate affect the pH of my buffer?

Yes, cadmium sulfate can affect the pH of your buffer solution. It is a strong acid and can lower the pH of the solution.

2. How does cadmium sulfate affect the pH of my buffer?

Cadmium sulfate dissociates in water to form cadmium ions and sulfate ions. The cadmium ions can react with water to form a strong acid, which can lower the pH of the buffer solution.

3. Can cadmium sulfate affect the pH of my buffer even in small amounts?

Yes, even small amounts of cadmium sulfate can significantly affect the pH of your buffer solution. It is important to carefully consider the concentration of cadmium sulfate when preparing your buffer solution.

4. How can I prevent cadmium sulfate from affecting the pH of my buffer?

You can prevent cadmium sulfate from affecting the pH of your buffer by carefully calculating the amount of cadmium sulfate to be added and using a suitable buffering agent. It is also important to regularly monitor the pH of your buffer solution and make adjustments if necessary.

5. Are there any safety precautions to consider when using cadmium sulfate in a buffer solution?

Yes, cadmium sulfate is a toxic substance and should be handled with caution. Always wear appropriate personal protective equipment and follow proper safety protocols when working with cadmium sulfate. It is also important to properly dispose of any leftover solution and clean up any spills immediately.

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