Question

What is the role of an indicator in an acid-base titration? In your answer, identify how an appropriate indicator is chosen and use the terms "end point" and "equivalence point" to explain how an indicator works.

Answer 1

Answer: indicate the end point of a titration

Explanation:

The indicators are substances that being weak acids or bases to be added to the sample on which the analysis is desired, there is a chemical change that is noticeable, usually a color change; this occurs because these unionized substances have a different color than when ionize .

The color variation is called a turn for this the indicator must change its chemical structure either by losing or accepting a proton.

This change in the indicator occurs because during the analysis a change in the conditions of the sample takes place and indicates the end point of the assessment. The operation and the reason for this change vary greatly depending on the type of assessment and indicator

On the other hand,  the point of equivalence of a valuation (another word for titration) is called the point at which equivalent amounts of reactive solution and the substance to be determined have been mixed. For example, in the case of titration of a solution of hydrochloric acid with a solution of sodium hydroxide, the equivalence point is reached when exactly one mole of NaOH is added for each mole of HCl. In this case the acidity of the resulting solution will be equal to that of pure water. We can't see it, but we can see the final point thanks to the indicator.

Answer 2

An indicator shows where the endpoint of a titration is.  Different indicators will change colors at different equivalence points.  Phenolphthalein will change colors at around pH7.5 or so, and others like Methylene Blue will change around a pH of 6.  Different titrations will have different pH's at different equivalence points.