Percent Ca as CaO?

**Did this part**Calculate the molar concentration of EDTA in a solution prepared by dissolving 7.5995g of the disodium salt of EDTA dihydrate in 500mL of water, assuming the EDTA salt is primary standard quality. MW = 372.240

**Need help here!**Calculate the actual molar concentration of this EDTA solution if 28.8mL of it is required to titrate 0.125g of primary standard CaCO3 (MW = 100.087).

Answer:
Do you still need help? I would need to know the actual formula for EDTA (I'm familiar with IUPAC nomenclature.) or at least how it reacts with CaCO3.

You determine the number of moles of CaCO3 that are in 0.125g (.0125g x mol/100.087g = 0.0012489 mol). Then use the balanced equation to determine the relationship between CaCO3 and your EDTA. If it's 1:1, then you would use an equal number of moles of EDTA as you used CaCO3. Then you divide this number of moles by the volume you titrated (0.0288L). This would give you the molarity of your solution. For 1:1, it would be 0.0433 M.

Does that help? Too late? Sorry!

Part A is 4.08E-2M

Here is the balanced equation :

2CaCO3+Na4(EDTA*2H2O>>
Ca2(EDTA)+2Na2CO3+2H2O

Use dimentional analysis

0.125g CaCO3 x (1moleCaCO3/100.087gCaCO3) x
cont'd (1mole Na4EDTA*2H20/2moles CaCO3)

(All units cancel but moles of Na4EDTA*2H2O) therfore

moles of NA4EDTA >>> 6.24E-4moles

then 6.24E-4moles Na4EDTA/0.028L = 2.23E-2 Molar soln

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Percent Ca as CaO?

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