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Olympiad workbook
Exam
Olympiad workbook
Subject
NSEC
Chapter
Redox Reactions

Olympiad workbook · NSEC · Redox Reactions

The table below gives the results of three titrations carried out...

The table below gives the results of three titrations carried out with 0.200 M HCl to determine the molarity of a given NaOH solution using phenolphthalein as indicator. NaOH was taken in the burette and HCl was taken in a conical flask for the titrations.
TitrationNo\begin{aligned}& Titration\\ & No\end{aligned} VHCl(mL)V_{HCl}(mL) VNaOH(mL)V_{NaOH}(mL) MNaOHmoldm−3M_{NaOHmoldm}{}^{-3}
I 21.4 19.3 0.222
II 18.6 16.8 0.221
III 22.2 21.1 0.210
The actual molarity of the prepared NaOH solution was 0.220moldm−30.220\mathrm{moldm}^{-3}. Which among the following could be the reason for the wrong value obtained in titration III?

Options

  1. ANumber of drops of phenolphthalein added to the titration flask was more in this titration
  2. BThe concentration of HCl was wrongly used as 0.250 M for the calculation of MNaOH\mathrm{M}_{\mathrm{NaOH}}
  3. CA few drops of NaOH solution were spilled outside the titration flask during titration
  4. DA few drops of the neutralized solution from titration II were left behind in the flask

Correct answer

C. A few drops of NaOH solution were spilled outside the titration flask during titration

Step-by-step solution

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