Question

Describe the difference between equivalence point and endpoint. For a monoprotic weak acid titrated with a strong base, are the two equivalent?

Answer 1

Equivalent point: The point at which the concentration of titrant is equal to the concentration of the analyte is called Equivalent point.

Endpoint: The indicator will not show any visible color change at the equivalent point. Almost every indicator's physical changes (color) is seen after the addition of a slight excess of titrant into analyte. The point at which indicator undergoes the color change is called Endpoint. The endpoint and equivalent point are not the same.

Titration error = Equivalent point - Endpoint

The titration error is very small. even it is in negligible amount.

Phenolphthalein transition range Bromothymol blue transition range Bromocresol green transition range 0 50 60 10 20 30 40 Volume of NaOH, mL

Titration curve of acetic acid Vs sodium hydroxide (weak acid Vs strong base). In this graph, the equivalent point is the midpoint of the sigmoid curve. As we know that, Endpoint is depends on the indicator, by changing the indicator the endpoint also changes. From this, you can conclude that the equivalent point and endpoint are not same.