introExploring Error in the Water Hardness Determinationby EDTA Titration ExperimentObjectives1.investigate the impurity of the calcium carbonateused to standardize the EDTA2.investigate the influence of magnesium and iron ionsconcentration in the water sample (water hardness calculator)CHM 103

CHM 103

impurity errorImpurities in the calcium carbonate used to standardize EDTATYPE:non-reactivemetal lower MMmetal higher MM10 g CaCO3percentreactedexampleimpuritymoles pureimpuritymoles impuretotal molesimpurity*non-reactive0.100000.00000.1000SiO2metal lower MM0.100000.00000.1000MgCO3metal higher MM0.100000.00000.1000SrCO3error factorpercenterror factorpercentmolarity EDTAerrorhardnesserrornon-reactive1.0000.001.0000.00metal lower MM1.0000.001.0000.00metal higher MM1.0000.001.0000.00How would Group B elements behave as impurities?How would Na2CO3 behave as an impurity?Sinex 2005* calculations based on these substances

non-reactive material lessens the moles of calcium carbonate by this amount of molesThe error increases due to the incorrect molarity being used to analyze the water sample. This is called the propogation of errors.Sinex 2005

water hardness errorHow does the Mg+2 and Fe+3 content influence the calculated water hardness?total moles titrated = moles Ca+2 + moles Mg+2 + moles Fe+3calculation of water hardness based on considering all CaCO3, since (Ca+2) > (Mg+2) >> (Fe+3)Enter concentrationsmg/Lmg/Lmg/Lin yellow cells:Ca+220Mg+20Fe+30moles Ca+2 =0.0005moles Mg+2 =0moles Fe+3 =0total moles = moles Ca+2 + moles Mg+2 + moles Fe+3 =0.0005(= moles EDTA by titration)calculated water hardness as CaCO3 =50mg CaCO3/L(soft water)actual water hardness* =50mg metal carbonates/Lpercent error =0.0%How does the Mg+2 concentration influence the water hardness? ...the Fe+3 concentration?Sinex 2005*actual water hardness considers the sum of masses of CaCO3, MgCO3, and Fe2(CO3)3

Sinex 2005