K2Cr2O7 was used to titrate a sample known to contain a mixt

K2Cr2O7 was used to titrate a sample known to contain a mixture of sodium sulfate (Na2C2O4) and sodium oxalate (K2C2O4). The dichromate does not react with sodium sulfate. 0.2487 g of the mixture was dissolved in dilute acid and titrated with the potassium dichromate solution to an endpoint at 12.61 mL. Calculate the percent by mass of sodium oxalate in the unknown mixture.

Solution

mols of Potassium dichromate:
0.01261 L. @ 0.022 mol/litre = 0.0002774 moles K2Cr2O7
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K2Cr2O7 & 6 electrons taken --> 2Cr+3

Na2C2O4 --> 2 CO2 & 2 electrons lost

balances electrons with tripling Na2C2O4:

1 K2Cr2O7 & 3 Na2C2O4 -->
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0.0002774 mol K2Cr2O7 @ 3 mol Na2C2O4 / 1 K2Cr2O7 = 0.0008323 mol Na2C2O4


0.0008323 mol Na2C2O4 @ 134.0 g/mol = 0.1115 grams Na2C2O4

0.1115 grams Na2C2O4/ A 0.2487 g mix =

your answer: 44.84 % Na2C2O4

now if you need to consider sig figs, I gave you a 4sigfig answer, & your problem had 4 sigfigs everywhere except when it came to the \"0.022M\" , or was it really 0.02200 Molar