a chemist titrates a monoprotic acid of known concentration and volume....

[baywatch123]

a chemist titrates a monoprotic acid of known concentration and volume with naoh of unknown concentration. By accident, he adds two extra drops of base after the endpoint of the titration is reached, but before measuring the volume of base used. What would be true about the concentration he calculates for the base?

a) it would be greater than the true value fo the base concentration
b) it would be less than the true value of the base concentration
c) it would be the same as the true value of the base concentration
d) it cannot be determined without knowledge of the strength of the acid
e) it cannot be determined wihtout the knowledge of the number of protons on the acid

*sigh* i thought i had this concept pat down, but apparently not

I said A but the answer is otherwise. i figured, if you added more base, the concentration of base would go up in a titration. i was assuming this was a strong acid and strong base titration?

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[Queen Beach]

B?

 

[DocDoon]

He calculates using measurements before the addition of the two extra drops. So the calculations are less than the true value (which includes the two extra drops) and B should be correct I think. Where is this question from?

 

[airstrikee]

I think it's B. The flask has a known concentration and volume of acid. Lets pretend that the acid has a concentration of 1M, and a volume of 1L. This means that there is 1 mol of monoprotic acid. To reach the endpoint titration, we need to add 1 mol of NaOH. Therefore, the concentration of the unknown = 1 mol of NaOH/volume of NaOH required to reach endpoint. Since the guy added two extra drops of NaOH, this will make the denominator larger - thus leading to a smaller value of concentration for NaOH.

 

[baywatch123]

Hi all, the question has been answered, but thank you for all your inputs. B is correct and this is a question from the princeton review mock exam for canada