A standard solution of sodium hydroxide can be used in a titration experiment to determine FW of unknown acid.

A common mistake is the failure to rinse the buret with the standard solution after the final water rinse but before measurements of volume of standard solution are taken. The mistake accounts for which results?


I. The volume of standard solution is reported too small.


II The volume of solute used to dissolve unknown acid is too small.


III. Number of moles of unknown acid is reported too large





a) I only


b) II and III only


c) III only


d) I and III only


e) I, II, and III

A standard solution of sodium hydroxide can be used in a titration experiment to determine FW of unknown acid.
After the final water rinse, there could be drops of water left in the biuret. Hence, when NaOH solution is poured into it to be measured, the drops of water causes the base to be diluted. So, the concentration of NaOH becomes smaller than what it should have been, which means that the no. of moles of base is lesser.





(I) cannot be the answer because the vol. is not affected.


(II) is also not the answer because the acid is not involved.





(III) is correct because as the concentration of NaOH is smaller (eg. 0.9mol/dm3) , a larger volume of NaOH is required to react with the acid. However, as it is thought that the concentration is higher (eg.1.0mol/dm3), it will be concluded that there is a larger no. of moles in the acid so that a larger volume of base will be needed for neutralisation.





so the answer is (c)





:D
Reply:Another Useless question.............who cares.....
Reply:do your homework!

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