1.) What is required to make a buffer solution? A weak acid and the salt of its
ID: 716414 • Letter: 1
Question
1.) What is required to make a buffer solution?
A weak acid and the salt of its conjugate base
A weak acid and a weak base
A strong acid and the salt of its conjugate base
A strong acid and a strong base
None of the above.
2.) Phosphoric acid has the formula H3PO4. How many different pKa values should you expect phosphoric acid to have?
1
2
3
4
The correct answer cannot be determined without additional information.
3.) Which of the following is not true of a compound with a large Ka value?
It is a strong acid.
It has a small pKa.
Most of the protons associated with it will dissociate in solution.
It has more than one donatable hydrogen associated with it.
4.) For any monoprotic compound, when does pH = pKa?
When the conjugate base concentration is much, much greater than the concentration of the acid.
When the acid concentration is much, much greater than the concentration of the conjugate base.
When the conjugate base concentration equals the acid concentration.
The answer cannot be determined without more information.
None of the above.
5.) Which of the following is not necessary when using a pH meter?
Calibrate the pH meter at the start of the experiment.
Rinse the electrode with deionized water each time prior to measuring pH.
Completely submerge the electrode or probe tip of the pH meter in teh solution being measured.
Neutralize the electrode with acid or base depending on whether you are measuring a basic or acidic solution, respectively.
All of the above must be done.
Explanation / Answer
1)
acidic buffer is formed by weak acid and salt of weak acid
basic buffer is formed by weak base and salt of weak base
Answer: A weak acid and the salt of its conjugate base
2)
Phosphoric acid (H3PO4) has 3 H
So, it will have 3 Ka values
Answer: 3
3)
large Ka implies stronger acid
Also,
pKa = -log Ka
So,
large Ka means smaller pKa
Answer: It has a small pKa
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