An eggshell is treated with NaOH to remove the membrane, dried and found to weigh 5.131 g. The shell is then dissolved in 25 mL of 6M HCI, filtered and diluted with distilled water to 250 mL in a volumetric flask. A 10.00 mL aliquot is buffered to pH 10 and titrated with 0.04916 M EDTA. If 40.78 mL is required to reach the Eriochrome black T endpoint signal, calculate the percentage of: (a) Ca, (b) CaCO3 in the eggshell.

A 50.00 mL aliquot of city drinking water was treated with a small amount of ammonia –- ammonium chloride buffer to bring the pH to 10. After the addition of EBT indicator the solution required 10.00 mL of 8.000 x 10-3 M EDTA for titration. Calculate the hardness in terms of parts per million calcium carbonate (100.0869 g/mol). O 80 160 ppm 320

A solution containing Mg2+ was buffered to pH 9.81 and titrated with EDTA. Eriochrome black T, with p?a1 = 6.3 and p?a2 = 11.6 was used as the indicator. It is a diprotic acid, H2E What is the fraction of the predominant form of eriochrome black T in solution at this pH? (To answer this, report the alpha fraction of the indicator’s most prevalent species at this pH)