First, they may produce direct and relatively short-lived effects, such as stimulation of the isolated uterus or relaxation of the isolated tracheal chain preparation.
Secondly, in doses too low to produce a direct effect, they may produce a long-term potentiation of the effects of other stimulants.
Letter C on the model titration curve corresponds to the point where pH equals the numerical value of pKa for HPr
<h3>What is a titration curve?</h3>
A titration curve is a graph of the pH of a solution against increasing volumes of an acid or a base that is added to the solution.
The pH of a solution is the negative logarithm to base ten of the hydrogen ion concentration and is a measure of the acidity or alkalinity of the solution.
The pKa is the acid dissociation constant of an acid solution.
In a titration of a strong acid and strong base, the pH at equivalence point is equal to the pKa of the acid.
The equivalence point is the point when equal moles of acids and base has reacted.
In the given titration curve, pH = pKa at point C.
In conclusion, for a titration curve of strong acid and base, at equivalence point, pH is equal to pKa of acid.
Learn more about equivalence point at: brainly.com/question/23502649
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Area measured in squares (or square units). We can count the squares or we can take the length and the width multiplication. The rectangle above has an area of 15 square units.