Question

A student titrates 25.00 ml. of tap water using 4.86 mL of 0.020 M EDTA. Calculate the hardness of the water

Answer 1

0.0038 M

Step-by-step explanation:

Hardness of the water is generally due to the presence of
`CaCO_3` in water.

At equivalence point

Moles of
`Ca^(2+)` = Moles of EDTA

Considering

`Molarity_(Ca^(2+))* Volume_(Ca^(2+))=Molarity_(EDTA)* Volume_(EDTA)`

Given that:

`Molarity_(EDTA)=0.020\ M`

`Volume_(EDTA)=4.86\ mL`

`Volume_(Water\ or\ Ca^(2+))=25.00\ mL`

So,

`Molarity_(Ca^(2+))* 25=0.020* 4.86`

`Molarity_(Ca^(2+))=0.0038\ M`