10 mL of tap water containing ca^(2+) and Mg^(2+) in the presence of HCO_(3)^(-)was properly buffered and the indicator mureside added . The sample was dilutedand heated to 60^(@)C.Titration with 0.01M EDTA solution changed the indicator colour at 7.50 mL . This complexed Ca^(2+) only . A second 10.mL sample was made basic and Erio T indicator added . Titration with 0.01M EDTAsolutionchanged the indicator colourat 13.02 mLUndertheseconditions both ca^(2+) and Mg^(2+) are complexed . If the 10 mLof water samplewere to be evaporated to dryness , what weight of CaCO_(3)+ MgCO_(3) would be formed?

10 mL of tap water containing ca^(2+) and Mg^(2+) in the presence of H

1.	10 mL of tap water containing ca^(2+) and Mg^(2+) in the presence of HCO_(3)^(-)was properly buffered and the indicator mureside added . The sample was dilutedand heated to 60^(@)C.Titration with 0.01M EDTA solution changed the indicator colour at 7.50 mL . This complexed Ca^(2+) only . A second 10.mL sample was made basic and Erio T indicator added . Titration with 0.01M EDTAsolutionchanged the indicator colourat 13.02 mLUndertheseconditions both ca^(2+) and Mg^(2+) are complexed . If the 10 mLof water samplewere to be evaporated to dryness , what weight of CaCO_(3)+ MgCO_(3) would be formed?
Answer» Solution :All EDTA cmplxesare FORMED on a ONE to one basis with dipositive ions . Mole f `Ca^(2+) +MG^(2+) ` = mole of `CaCO_(3)` + mole of `MgCO_(3)` `= (0.01 xx13.02)/(1000) = 13 xx 10^(-5)` Mole of `Ca^(2+) ` mole of `CaCO_(3)` `= (0.01 xx 7.50)/1000 = 7.50 xx10^(-5)` ` :. ` mole of `MgCO_(3) = 13 xx 10^(-5) - 7.50 xx10^(-5) = 5.5 xx 10^(-6)` ` :. `weight of `CaCO_(3) +MgCO_(3)= 7.50 xx10^(-5) xxx100 + 5.5 xx10^(-5) xx 84` ` = 1.21 xx 10^(-2) g ` `(CaCO_(3) = 100 , MgCO_(3)=84)`