How can we determine the equivalence point from the titration curve?
Answers:
Quick answer: The steepest part of the graph. Note: there may be a steep point at the beginning of the curve--ignore this. Look at the steep part on the right side of the graph.
If you have had calculus, somebody should be able to explain why you want the steepest point in terms of derivatives and inflection point.
Generally, after you neutralize all of the unknown, the pH of the unknown solution will start approaching the pH of the titrant.
Find out the slope.
A typical titration curve will be sigmoidal and if the reaction involved is 1:1 the equivalence point can be found by measuring the length of the steep part of the curve, dividing that length by 2 and then dropping from that point to the volume axis (x-axis).
Hope that helps.
In simple terms, mark half way down the steep (almost vertical) portion of the curve. Then read off the volume added at that point.
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