A certain acid is titrated by 0.100 M NaOH. A graph of pH vs. mL of titrant is s
ID: 865880 • Letter: A
Question
A certain acid is titrated by 0.100 M NaOH. A graph of pH vs. mL of titrant is shown for this titration
.Referring to the table below, which of the indicators listed in the table below would be good choice to use in the titration in order to detect the equivalence point with a minimal error?
Indicator Color Change pH Change in Which Color Change Occurs
Methyl violet Yellow to violet 0.0 - 1.6
Methyl red Red to yellow 4.8 - 6.2
Phenolphthalein Colorless to pink 8.2 - 10.0
Alizarin yellow Yellow to red 10.1 - 12.0
Select one:
A. Methyl red
B. Phenolphthalein
C. Methyl violet
D. All listed indicators are equally suitable.
E. Alizarin yellow
14 13 12 10F pH 10 20 30 40 50 mL of titrant (0.100 M NaOH)Explanation / Answer
answer : option B) Phenolphthalein
the above graph reveals it is titration of a weak acid by a strong base
the pH range in which the rapid change is seen occurs from about pH 7 to pH 11. that the pH range is shorter than that for the titration of strong acid by strong base. this means that the choice of a indicator is more critical . Phenolphthalein would work . it changes color in the range 8.2 to 10.0. remaining indicators would not work
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