Question

Would be there any effect on an experiment ( Dissolving CaCl2 and Na2CO3 in distilled water to calculate the yield of calcium carbonate) if tap water containing calcium ions is used insted of deionized water to dissolve reactants ? Explain.

Answer 1

Recall that

Na2CO3 --> soluble

CaCO3 --> not soluble

if we try to find --> CaCO3 content

then we will have the next side reaction

when dissolving

Na2CO3 --> CO3-2 is present in solution

if the water has ions, since it is tap water, then Ca+2 is present

Ca+2 + CO3-2 = CaCO3(s) will precipitate

NOTE that this should not happen, since these cations of Calcium come from external source

therefore, the CaCO3 mass will be higher than it should be

the % CaCO3 increases, in sample, or overall yield, since CaCO3 increased (incorrectl)