A 30.00 mL sample of 0.0100M MgEDTA2- solution was added to a 30.00 mL sample containing...

A 30.00 mL sample of 0.0100M MgEDTA^2- solution was added to a 30.00 mL sample containing Fe³⁺. The solution was then buffered to pH 10 and titrated with 12.83 mL of 0.0152 M EDTA to an Eriochrome Black-T endpoint. What was the [Fe³⁺] in the original sample?

Please show work.

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Expert Solution

First, we find the initial moles of Mg(EDTA)2 using the molarity equation

After the reaction of MgEDTA with Fe+3 ions, the excess of Mg+2 ions will be titrated with the 12,83mL of EDTA 0,0152M.

Now, we find the excess moles of Mg+2 who were titled with the EDTA.

At the endpoint, the moles of EDTA and Mg + 2 is the same.

Now, the difference between the initial moles and the excess moles gave us the moles of Fe+3 that react.

Finally, we find the initial concentration of 0,105mmoles of Fe+3 in 30mL of solution.

The [Fe+3] in the original 30mL sample was 3,5.10^(-3)M.

Note: The pH was brought to 10 so that the formation of the complex was carried out.

queen_honey_blossom answered 6 months ago

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