Student X titrated 25 cm\(^{3}\) of Na\(_{2}\)CO\(^{3}\) with 0.1 mol dm\(^{-3}\) HCI, using methyl orange...

WAEC 2021

Student X titrated 25 cm\(^{3}\) of Na\(_{2}\)CO\(^{3}\) with 0.1 mol dm\(^{-3}\) HCI, using methyl orange as indicator. Student Y carried out the same exercise but used phenolphthalein as an indicator. Which of the following statements about the titration is true?

A. hydrogen chloride gas was released in the reactions in both titrations
B. the titer values obtained from the titration are equal
C. the titer value obtained by X is twice that of Y
C. the titer value obtained by Y is twice that of X

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Correct Answer: Option C

Explanation

The titration of sodium carbonate (Na\(_2\)CO\(_3\)) with hydrochloric acid (HCl) occurs in two distinct stages due to the dibasic nature of the carbonate ion.

Because Student X (using methyl orange) titrates through both stages and Student Y (using phenolphthalein) titrates through only the first stage, Student X requires twice the volume of acid to reach the endpoint compared to Student Y.

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