8. After discovering that the chemistry storeroom was outof ‘primary standard, K

Question

8. After discovering that the chemistry storeroom was outof ‘primary standard, KHP’, the CHM 144 Instructordecided to substitute oxalic acid dihydrate (OAD;H2C2O4·2H2O) for the standardizationof

NaOH solution. The molecular equation for the titrationis:

H2C2O4·2H2O (aq) + 2NaOH(aq) ??Na2C2O4 (aq) +4H2O (l)

The following titration data were recorded byLucas:

Mass of OAD = 0.454 g

initial buret reading = 1.33 mL

final buret reading = 40.07 mL

molar mass of OAD = 126 g/mol

Use this data to calculate the molarity of the NaOHsolution.

A) 0.0929 M

B) 0.186 M

C) 0.0870 M

D) 0.174 M

E)0.0465 M

Explanation / Answer

n(H2C2O4·2H2O ) = 0.454/126 = 0.003603mol n(NaOH) = 2/1 x n(H2C2O4·2H2O ) = 0.007206mol Total volume of used = 40.07 - 1.33 = 38.74mL c(NaOH)= n/v = 0.007206/0.03874 = 0.186M Hope this helps!

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