Hardness $($EDTA$)$ mgCaC$\frac{O^3}{L}=\frac{AN50,000}{(mL)\text{s}\text{a}\text{m}\text{p}\text{l}\text{e}}$

Where:

$A=mL$ EDTA titrant $(6\mathrm{.}4)$

$N=$ normality of EDTA titrant

$50\mathrm{.}0mL$ tap water sample.

$13\mathrm{.}75mL$ EDTA used in the titration.

a$)$ Calculate the moles of EDTA used.

b$)$ Calculate the molarity of metal ion present in the tap water

sample $($Remember: EDTA binds to metal ions on a $1$:$1$ molar

ratio$).$

c$)$ Find the ppm calcium ion concentration in the sample based

on your results from question b$).$