Titration of Zinc with EDTA

[anon13]

Homework Statement

I'm trying to determine the percentage of zinc in an unknown sample. What I did in this lab, was, I titrated the zinc solution (which contained about 4g unknown zinc sample) with Na2EDTA and it took about 20 mL to reach the end point. Before doing this, I standardized the Na2EDTA solution by using the Na2EDTA to titrate a calcium standard solution which contained about 0.25 g of calcium carbonate. It took about 25 mL to titrate this. So now my question is, how do I find the percentage of zinc in the unknown sample?

Homework Equations

n=m/M, n= CxV

The Attempt at a Solution

I found the standardized concentration of Na2EDTA which is 0.1 M. So how do I use this standardization to find the amount of zinc in the sample?

 

[symbolipoint]

For ease of giving help, I ignore the standardization process.
Moles of Zinc titrated is equivalent to moles of EDTA used for titration.
Moles of Zinc = (0.020 liters of EDTA solution) * (0.1 moles EDTA/liter EDTA solution)