What volume of 2.138*mol*L^-12.138molL1 NaOHNaOH is required to react with a 25.0*mL25.0mL volume of 0.3057*mol*L^-10.3057molL1 solution of "potassium pthalate"potassium pthalate, 1,2-C_6H_4(CO_2H)(CO_2^(-)K^(+))1,2C6H4(CO2H)(CO2K+)?

1 Answer
Mar 2, 2017

Approx. "3.6"*"mL"3.6mL.

Explanation:

We need (i) a stoichiometrically balanced equation to represent the acid-base reaction (this should always be your priority in these types of questions!):

"NaOH(aq)" + "1,2-C"_6"H"_4("CO"_2^(-)"K"^(+))"CO"_2"H"rarr"1,2-C"_6"H"_4("CO"_2^(-)"K"^(+))("CO"_2^(-)"Na"^(+)) +"H"_2"O"NaOH(aq)+1,2-C6H4(CO2K+)CO2H1,2-C6H4(CO2K+)(CO2Na+)+H2O

There is thus "1:1 equivalence"1:1 equivalence between "moles of sodium hydroxide"moles of sodium hydroxide, and "moles of KHP."moles of KHP.

And now (ii) we need to find the equivalent quantites of each reagent:

"Moles of potassium bipthalate,"Moles of potassium bipthalate, 0.3057*mol*cancel(L^-1)xx25.0*cancel(mL)xx10^-3*cancelL*cancel(mL^-1)
=7.643xx10^-3*mol.

And thus volume of standardized "NaOH(aq)" required is:

(7.643xx10^-3*cancel"mol")/(2.138*cancel"mol"*cancel("L"^-1))xx10^3*mL*cancel("L"^-1)=3.58*"mL"

Do you think it would have been better to have used 0.2138*mol*L^-1 "NaOH(aq)" instead of 2.138*mol*L^-1 "NaOH(aq)" for this titration? Why, or why not?