2.0124 g milk powder sample was dissolved in water and the Ph of the solution was adjusted to 10. 30 cm^3 of a 0.03210 mol/dm^3 EDTA solution was added. the excess EDTA was complexed with 7.25cm^3 of a 0.01250mol/dm^3 Mg2+ solution. Calculate the % Ca(Mr=40.078g/mol) in the sample.
First, we need to calculate the amount of Ca in the sample using the EDTA titration reaction:
Ca2+ + EDTA → CaEDTA2-
From the reaction stoichiometry, 1 mole of Ca2+ reacts with 1 mole of EDTA.
Moles of EDTA = 0.03210 mol/dm^3 x 0.03 dm^3 = 0.000963 mol
Moles of Ca2+ = Moles of EDTA = 0.000963 mol
Now, we can calculate the mass of Ca in the sample:
Mass of Ca = Moles of Ca2+ x Mr of Ca = 0.000963 mol x 40.078 g/mol = 0.03865 g
Finally, we can calculate the percentage of Ca in the sample:
% Ca = (Mass of Ca / Mass of sample) x 100
% Ca = (0.03865 g / 2.0124 g) x 100
% Ca = 1.92%
Therefore, the percentage of Ca in the milk powder sample is 1.92%.