What would be the % calcium in a leafy vegetable extract applying 30.50 grams sample absorbing 9.8 mL of 0.0575 M EDTA solution?

Question

I had a hard time solving this because our given formula is shown like this:

% = V x M.F. x titer value / Wt(mg) ÷ MW x 100

I do not know how to identify the M.F. and the titer value based on the given problem that's why I am stuck solving this.

Answer 1

That's kind of a gross formula but it is written for the values you are given except they specify mg of sample have to used in the formula (.0575)(9.8)/40.08/30500 * 100

This is not good. There is no appreciation of units needed or how this is calculated:

1) Find the percentage of Ca in the sample by finding the fraction of Ca and dividing by the mass of sample (x 100 for decimal to percent)

2) To find the mass of calcium (1:1 with EDTA) go from moles of EDTA to moles of Calcium to grams of Calcium:

9.8 ml EDTA * 1liter/1000ml * .0575 mole/liter * 1 mole Ca/mole EDTA * 40.08 g/mole Ca = g Ca

Going back to 1) g Ca/g Sample * 100 is % Ca

The formula works because they did not multiply the molarity by liters (ml instead) and corrected this by dividing by milligrams instead of grams which cancels the error.

Take care.