hingwood asked in 科學及數學化學 · 1 decade ago

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A standard solution of sodium carbonate is used to to find the concentration of some hydrochloric acid. 20.00mL aliquots of the sodium carbonate are pipetted into conical flasks and titrated against the acid using methyl orange as indicator.

ii) Would these actions affect their final result?

Adding 10 drops of indicator instead of 3 drops

Using a wet conical flask instead of a dry one?

1 Answer

  • 1 decade ago
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    “Adding 10 drops of indicator instead of 3 drops”

    Methyl orange indicator is a weak acid. Theoretically, if more drops of methyl orange are added, less acid is required due to the presence of more acidic indicator in the solution.

    Actually, the effect is negligible because the weakly acidic methyl orange indicator is very dilute.


    ”Using a wet conical flask instead of a dry one”

    There is no effect on the end-point of the titration. This is because the presence of water of water does not affect the number of moles of Na2CO3 added to the conical flask, and this lead to the volume of acid added from the burette remains unchanged.

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