Finding calcium concentration in milk using EDTA titration

[kkln1212]

Homework Statement

A sample of powdered milk weighing 1.450 g was mixed with an aqueous buffer of pH 11.5. A few drops of Calagmite indicator were added and the solution required 31.62 mL of 1.539x10^-2 M EDTA to reach the end-point color change.

a. Calculate the concentration of calcium in the milk.
b. Why does the solution need to be buffered?

Homework Equations

M1V1 = M2V2

The Attempt at a Solution

I really don't know how to solve this problem

 

[Borek]

In general all titration questions are identical:

http://www.titrations.info/titration-calculation

 

[chemisttree]

EDTA complexes 1:1 with calcium. Calagmite turns red when it is added to the milk by complexing with free calcium until enough EDTA is added to grab it away. When enough EDTA has been added, the calcium-free indicator fades to colorless.