MCQ for PCR Mixture Preparation

Question 1: A buffer solution consists of a mixture of __________ and ________.

acid, base
INCORRECT. Please try again.
weak acid, weak base
INCORRECT. Please try again.
weak acid, its conjugate base
CORRECT. A buffer solution consists of a mixture of weak acid and its conjugate base.
weak acid, water
INCORRECT. Please try again.

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Question 2: Use Henderson-Hasselbalch equation with pH=7.00 and pK_a=7.20, calculate the ratio of conjugate base/weak acid.

0.62
INCORRECT. Please try again.
0.63
CORRECT! Use Henderson-Hasselbalch equation pH=pK_a + log {[conjugate base]/ [weak acid] } to calcuate, the answer is 0.63.
0.64
INCORRECT! Please try again.
0.65
INCORRECT! Please try again.

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Question 3: Which of the following statement is/are true?
I. If the pH is monitored as base is added to weak acid in the course of a titration, an inflection point is reached when the pH= pK_a
II. In the action of buffer, adding OH^- converts HA to A^-
III. In the action of buffer, adding H⁺ converts OH^- to H₂O

I only.
INCORRECT. Please try again
I and II only.
CORRECT. Statement III is false. In action of buffer, adding H⁺ converts A^- to HA, but not converts OH^- to H₂O
II and III only.
INCORRECT! One of them is false. Please try again.
All of the above.
INCORRECT! One of them is false. Please try again.

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Question 4: Which of the following statement is/are true?
I. Timer
II. Hemocytometer
III. Microscope

I only.
INCORRECT. Bases are proton acceptors but not proton donors. Please try again.
II only.
INCORRECT. One more statement is true. Please try again.
II and III only.
CORRECT. Only statement I is false.
I and III only.
INCORRECT. Timer is not required. Please try again.

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Question 5: Which of the following is Not a criterion for selection of buffer?

Select the one with a pK_a=7.
CORRECT. It is not necessary to select buffer with pK_a=7. Just select the one with a pK_a as near as possible to the required experimental pH.
Select an appropriate concentration of buffer to have adequate buffer capacity for the particular experiment.
INCORRECT. It is one of the criteria for selection of buffer. Please try again.
Ensure that the selected buffer does not form insoluble complexes with any anion or cation for the reaction being studied.
INCORRECT. It is one of the criteria for selection of buffer. Please try again.
Ensure that the proposed buffer has other desirable properties such as being non-toxic.
INCORRECT. It is one of the criteria for selection of buffer. Please try again.

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Finish!

MCQ for Preparation of phosphate buffer