Chemistry 5070 · O Level · Acid–base titrations

Acid–base titrations — practice question

Two titrations involving dilute hydrochloric acid and aqueous sodium hydroxide are carried out with two different indicators, methyl orange and thymolphthalein. The reaction equation is given below. $\text{HCl(aq)} + \text{NaOH(aq)} \rightarrow \text{NaCl(aq)} + \text{H}_2\text{O(l)}$ A volumetric pipette is used to transfer $25.0\,\text{cm}^3$ of dilute hydrochloric acid into a conical flask containing a few drops of indicator. Aqueous sodium hydroxide is then delivered from a burette into the dilute hydrochloric acid until the end-point is reached. For each indicator, the end-point occurs when $23.6\,\text{cm}^3$ of aqueous sodium hydroxide has been added. Which of the following statements about this experiment are correct?

  • A1, 2 and 3
  • B1 and 2 only
  • C1 and 3 only
  • D2 and 3 only

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