Titration Lab Question, I don\'t know how to draw a molecular level picture, the

Question

Titration Lab Question,

I don't know how to draw a molecular level picture, the professor is looking for the molecular level pic in the beaker before at half point at equivalent point and at end point of titration according to her email I received. The question is as following.

1) Draw a molecular level picture (showing Na+, H+, OH -, H2O, etc…) of what is in your beaker before, at half point, at equivalent point, and at end point of the titration.

My equation for first test is with acid and base ,

NaOH(aq)+HA(aq)?NaA(aq)+H2O(l)

Second test with KHP solution is ,

NaOH(aq) + KHP(aq) ---> KNaP(aq) + H2O(l)

Please help me out, I must turn this in tomorrow.

Explanation / Answer

Hi,

Answer # 1) You have HA (aq) in the beaker which will dissociate as:

H3O+ and A- -> this you can write as "in the beaker before"

Now at the equivalent point, NaOH (aq) sould completely consume all the HA (aq) and hence "at the equivalence point" you will have --> Na+ (aq) , A- (aq) and H2O (aq) . Note that NaA will dissociate in water.

At the end point you will have same molecular entities like equivalence point, additionally, OH- (aq) will also be present due to excessive amount of NaOH (aq) added to the beaker.

Answer # 2) KHP will be present as :

K+ (aq) and HP- (aq) "in the beaker before" since it dissociates completely in water.

At the equivalence point, the beaker should contain:

K+ (aq), Na+ (aq), H2O (aq) and phthalate dianion (P2-) (aq).

At the end point, the beaker will have all the species present at equivalence point and also the OH- (aq) due to presence of excessive NaOH in the solution.

Thanks, please share your valuable feedback . Hope this will be helpful to you.

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