Buffer Preparation Problem

In summary, the problem is to prepare a 500mL buffer solution with a pH of 12.50 and a concentration of at least 0.10 M, using the reagents of solid sodium dihydrogen phosphate dihydrate, distilled water, 1.00 M NaOH(aq), and 1.00 M HCl(aq). The Henderson-Hasselbach equation cannot be used since equilibrium constants are not given, but the NaH2PO4 can act as the buffering agent. However, creating an alkaline buffer solution with a strong acid and strong base may not be possible due to the rule that an acid with two more oxygens than hydrogens is considered a strong acid.
  • #1
Erinyes83
1
0
Got a tough problem I have no clue how to do.

I have to prepare 500mL of a buffer solution with a pH of 12.50 and must be at least .10 M.

The only reagents I have are:
solid sodium dihydrogen phosphate dihydrate NaH2PO4 x (H2O)2
Distilled water
1.00 M NaOH(aq)
1.00 M HCL(aq)

Not all reagents need to be used. If I could get some help on how to do this problem, anything would be aprreciated.
 
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  • #2
did you try the henderson-hasselbach equation?
 
  • #3
Hederson-Hasselbach wouldn't work because you don't have any of the equillibrium constants such as Ka and Kb
I think its impossible because strong acids and strong bases don't create buffer solutions
 
  • #4
Equilibrium constants can be looked up in chemistry books, and the NaH2PO4 is the buffering agent. The strong acid and strong base are for equilibrating it to the right buffering pH.
 
  • #5
I see it now, my apologies, Henderson-Hasselbach would be in order. I believe the NaH2PO4 would ionize in water to form Phosphoric Acid and Sodium Phosphate. Then of course using the equation aformentioned to determine the pH. Then I'm afraid that i am baffled, because that would be an acidic buffer solution, and following a rule that was taught to me, an acid with 2 more oxygens then hydrogens is a strong acid, but there are exceptions and this may be one of them.
 

1. What is a buffer solution?

A buffer solution is a solution that resists changes in pH when small amounts of strong acid or base are added to it. It contains a weak acid and its conjugate base, or a weak base and its conjugate acid, which react to maintain a relatively constant pH.

2. Why is buffer preparation important?

Buffer preparation is important because it allows scientists to control and maintain a specific pH level in a solution. This is critical in many biological and chemical experiments, as certain reactions or processes only occur within a specific pH range.

3. How do you prepare a buffer solution?

To prepare a buffer solution, first determine the desired pH and the pKa of the weak acid or base that will be used in the buffer. Then, mix the weak acid or base with its conjugate salt in a specific ratio, known as the Henderson-Hasselbalch equation, to achieve the desired pH.

4. What are the common sources of error in buffer preparation?

The most common sources of error in buffer preparation include inaccurate measurement of the chemicals, incorrect calculation of the Henderson-Hasselbalch equation, and contamination of the solution. It is important to use precise measuring instruments and follow proper lab techniques to minimize these errors.

5. Can buffer solutions be stored for later use?

Yes, buffer solutions can be stored for later use. However, it is important to keep the solution tightly sealed to prevent evaporation or contamination. It is also recommended to periodically check the pH of the stored buffer solution and adjust if necessary.

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