Does the equivalence point in a titration always have a pH of 7?

Question

In a titration, I know that the equivalence point is: 'the point at which the volume of one solution has reacted exactly with the volume of the second solution'

But does that mean that because this is the point at which an acid has completely reacted with an alkali, the pH should be neutral at this point? And just the volumes of the acid and alkali vary?

Or does the pH of each equivalence point vary depending on the strength of the acid or alkali?

Answer 1

The overall answer to your question is no. Now, some explanation.



Your statement of the equivalence point and C6H6's are both incorrect.



The equivalence point is reacted when stoichiometric amounts of the acid and base have reacted. In your answer, you spoke of volumes. The volumes used may vary. C6H6 spoke of one mole and one mole. This is not correct because you can can certaily have less than (or more than) one mole reacting.



Also, C6H6 is incorrect, in that the stoichiometric ratio between HCl and Ba(OH)2 reacting is two moles of HCl are needed to exactly neutralize one mole of Ba(OH)2.



An equivalence point of 7 is reacted only when a strong acid (HCl) reacts with a strong base (NaOH).



There are three other cases:



1) strong acid - weak base

2) weak acid - strong base (the most popular one in problems)

3) weak acid - weak base



In the first one, the pH of the equivalence point will be acidic (below 7). In the second, the pH at the equivalence point will be basic (above 7). In the third case, the Ka and Kb must be known and the equivalence point pH is determined by which one is stronger (or weaker). The third case is not usually addressed in introductory classes.



The pH of the equivalence point in cases 1 and 2 just above are created by the hydrolysis of the salt of the titration products.



If acetic acid and NaOH are titrated, sodium acetate is formed. In solution, the acetate ion does this:



CH3COO^- + H2O ---> CH3COOH + OH^-



The acetate ion, by its presence in solution, upsets the amount of hydroxide in pure water, causing it to increase, thereby creating a basic pH value at the equivalence point.



If ammonia and HCl are titrated, this happens:



NH4^+ + H2O ---> NH3 + H3O^+



HTH

Answer 2

even even if it really is easily neutralised the pH would not be 7. the perception of pH=7 is named a crude assumption. i imagine you do not comprehend the that technique of pH even if it can suffice to assert that pH of a impartial substance (eg. deionised water) is in common words 7 at 24 degree centigrade and there are acidic salts and effortless salts (eg. ammonium nitrate and sodium citrate) that had different pH values except 7 at the same time as neutralised.

Answer 3

No, the equivalence point is a function of the pK for the acid-base pair that is being titrated for. Each acid-base pair has an equilibrium point that is specific to the substance.



Only water has a equivalence point of 7 (or is it half equivalence, I forget) because the pK for water is 14, and H+=OH- where pH=7 : (H+)*(OH-)=10^-14 or (H+)=squareroot (10^-14)=10^-7



If you substitute acetate, or sulfate for OH- in those reactions, the pK has to be different, and the point where H+=anion is therefore at a different pH.

Answer 4

In a titration, you know that the equivalence point is: 'the point at which one mole of hydrogen ions (H^+) of the first solution has reacted exactly with one mole of hydrogen ions (OH^-)the volume of the second solution.



That means the point at which an acid has completely reacted with an alkali, the pH will be neutral at this point, pH = 7. And just the volumes of the acid and alkali vary? No, the both volumes do not vary



Or does the pH of each equivalence point vary depending on the strength of the acid or alkali? No, it doesn’t, since the pH is always 7.



Bye,



C6H6