An edta solution was prepared by dissolving 3.7015g of disodium acid dihydrate (mw=372.3) in enough water to make 100ml of solution a .01732g portion of a solid sample which contained copper(ii) was dissolved in 100 ml of a ph 2 bufer solution. the endpoint of the titration was 9.98ml. calculate the percent copper in the solid sample.

The percent copper in the solid sample is 27.5 %

Explanation:

Step 1: The balanced equation

Cu + EDTA → Cu-EDTAcomplex

Step 2: Given data

mass of disodium acid dihydrate (EDTA) = 3.7015g

Molar mass of EDTA = 372.3 g/mol

volume of the solution = 100 mL

mass of the copper(II) containing sample = 0.01732g

pH of the solution = 2

The endpoint of the titration = 9.98mL

Step 3: Calculate number of moles of EDTA

Moles = mass of EDTA / Molar mass

moles = 3.7015g /372.3g/mol

moles = 0.00994 moles

Step 4: Calculate molarity of EDTA

Molarity of EDTA = number of moles / volume of EDTA

Molarity = 0.00994 moles / 0.1 L = 0.0994 M

Step 5: Calculate moles of Cu

moles = molarity * volume

moles = 0.0994 M * 0.00998L = 0.000992 moles

Step 6: Calculate mass of Cu

Mass of Cu = moles of Cu * Molar mass of Cu

mass of Cu = 0.000992 moles * 63.546 g/mol

mass of Cu = 0.063 grams

Step 7: Calculate the procent copper

(0.01732 grams/ 0.063 grams) = 27.5%

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your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.