Explain how each of the following errors would have altered your results. Clearl
ID: 499016 • Letter: E
Question
Explain how each of the following errors would have altered your results. Clearly explain why your calculations would be high, low, or unchanged. (A single word answer is not acceptable.) a. The pH buffers used to calibrate the pH meter were each 0.5 pH units low (3.5 and 6.5 rather than 4.0 and 7.0 respectively). b. You decided to take the pH after each addition of 5.0 mL of NaOH rather than after every 0.5 mL during the neutralization of your acid sample. c. While using the Half Volume method, your solution was dark pink (you overshot the endpoint) and you added the unreacted acid to this solution. d. You refilled your buret between titrations of your unknown acid. Instead of using 0.1 M NaOH as you did for the first titration, you used 0.2 M NaOH.Explanation / Answer
a) The pH buffers used to calibrate the pH meter were each 0.5 pH units high (4.5 and 7.5 rather than 4 and 7 respectively).
Answer: Since the pH meter is calibrated at a higher pH, the pH calculated will be higher than actual pH of solution
b) You decided to take the pH after each addition of 5 mL of NaOH rather than after every 0.5 mL during the neutralization of your acid sample.
Answer: After neutralization, the addition of strong base will cause a sharp increase in pH.Thus, 0.5 mL of NaOH will be sufficient to cause a sharp increase in pH. The pH meter will not be able to distinguish between the addition of 0,5 mL or 5mL.Thus, the answer is unchanged
c) While using the Half Volume method, your solution was dark pink (you overshot the endpoint) and you added the unreacted acid to this solution.
Answer: Since more volume is added and considered for calculation, the calculated concentration of base (solution) will be higher than the actual concentration
d) You refilled your burette between titrations of your unknown acid. Instead of using 0.1 M NaOH as you did for the first titration, you used 0.2 M NaOH.
Answer: Here calculations are done using a false higher concentration of one reagent. Thus, the calculated concentration will be less than the actual
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