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Correct Answer: the ph of the endpoint depends upon the indicator used.
the correct statement concerning an acid-base titration is: "the ph of the endpoint depends upon the indicator used." this statement is true because different indicators change color at different ph levels. in an acid-base titration, the choice of indicator is crucial as it must be appropriate for the ph range at which the color change should occur, indicating the endpoint of the titration. this endpoint ideally should be close to the equivalence point, where the amount of acid equals the amount of base, but the actual ph at which the indicator changes color can vary depending on its chemical properties.
it's important to note that the equivalence point and the endpoint are related but distinct concepts. the equivalence point is a stoichiometric concept where the moles of acid and base in the solution are equal, and this point is dictated by the reaction's stoichiometry, not by the indicator. the endpoint, on the other hand, is a practical observation based on the indicator's color change. therefore, while the endpoint should ideally align with the equivalence point, the ph observed at the endpoint actually depends on the nature of the indicator used.
moreover, the statement "the ph of the equivalence point depends upon the indicator used" is incorrect. the ph at the equivalence point is determined by the strengths and concentrations of the acid and base involved in the titration, not by the indicator. for example, titrating a strong acid with a strong base typically results in an equivalence point at ph 7. however, if a weak acid or base is involved, the equivalence point ph can be less than or greater than 7, depending on the specific acid and base's dissociation constants.
the statement "the solution will always be neutral (ph 7.0) at the equivalence point" is also not universally true. as previously noted, only the titration of strong acids with strong bases results in a neutral solution at the equivalence point. in cases involving weak acids or bases, the ph at the equivalence point deviates from 7.0 due to the incomplete dissociation of the weak acid or base.
lastly, the claim "using a higher concentration titrant will result in more titrant being needed to reach the endpoint" is incorrect. in fact, using a higher concentration of titrant typically means that less volume is needed to reach the equivalence point because each drop of titrant contains more moles of titrant, effectively neutralizing more moles of the analyte per unit volume. hence, a higher concentration titrant decreases the volume required to reach the endpoint, assuming the amount of analyte is constant.
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