2.0124 g milk powder sample was dissolved in water and the ph of the solution was adjusted to 10.30.00 cm^3of 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.
To calculate the % Ca in the sample, we need to determine the amount of Ca present in the sample based on the titration results.
Step 1: Calculate the moles of EDTA used in the titration
Moles of EDTA = molarity x volume (L)
Moles of EDTA = 0.03210 mol/dm^3 x (10.00/1000) L
Moles of EDTA = 3.210 x 10^-4 mol
Step 2: Calculate the moles of Mg2+ complexed with excess EDTA
Moles of Mg2+ = molarity x volume (L)
Moles of Mg2+ = 0.01250 mol/dm^3 x (7.25/1000) L
Moles of Mg2+ = 9.063 x 10^-5 mol
Step 3: Determine the moles of Ca complexed with EDTA (Ca:EDTA ratio is 1:1)
Moles of Ca = Moles of EDTA - Moles of Mg2+
Moles of Ca = 3.210 x 10^-4 mol - 9.063 x 10^-5 mol
Moles of Ca = 2.3037 x 10^-4 mol
Step 4: Calculate the mass of Ca in the sample
Mass of Ca = Moles of Ca x molar mass of Ca
Mass of Ca = 2.3037 x 10^-4 mol x 40.078 g/mol
Mass of Ca = 9.2366 x 10^-3 g
Step 5: Calculate the % Ca in the sample
% Ca = (Mass of Ca / Mass of sample) x 100
% Ca = (9.2366 x 10^-3 g / 2.0124 g) x 100
% Ca = 0.4590 x 100
% Ca = 45.90%
Therefore, the % Ca in the milk powder sample is 45.90%.