1. What effect would the following errors have on the calculated value of Ka? Ch
ID: 905095 • Letter: 1
Question
1. What effect would the following errors have on the calculated value of Ka? Choose
whether the calculated value would be too high, too low, or if there is no effect. Explain your
Answer.
a. The pH meter was improperly calibrated, so that the pH readings on the instrument
were 0.3 pH units too low.
A. pKa would be too low and Ka would be too high
B. pKa would be too high and Ka would be too low
C. neither would change
D. none of these
Explanation:
b. An endpoint/equivalence point was erroneously read as 27.20 mL whereas the reading
was actually 26.80 mL.
A. pKa would be too low and Ka would be too high
B. pKa would be too high and Ka would be too low
C. neither would change
D. none of these
Explanation:
c. In Step 2, instead of adding 75 mL of water, 150 mL of water was added.
A. pKa would be too low and Ka would be too high
B. pKa would be too high and Ka would be too low
C. neither would change
D. none of these
Explanation:
Explanation / Answer
1.
(a) Sol : C.Neither would change
Explanation : Since the improper calibration of pH meter just shows the wrong pH value only , it does not determines the dissociation of ions of the . Which shows that Ka is not affected and also the pKa of the solution
(b) Sol : B.pKa would be too high and Ka would be too low
Explanation : Error found was actually more than the actual value , then eventually the dissociation constant (Ka) decreases than the actual dissociation value , which in turn results in high pKa value.
(c)Sol : B.pKa would be too high and Ka would be too low
Explanation : dissociation constant (Ka) decreases than the actual dissociation value
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