49 PRE-LAB Exercise 1. A standard calcium solution was prepared by quantitativel

Question

49 PRE-LAB Exercise 1. A standard calcium solution was prepared by quantitatively transferring 0.3412 grams of CaCOs to a 500 mL volumetric flask. After wetting the CaCOs with a small volume of deionized water, a sufficient amount of concentrated HCI was added to dissolve the carbonate; and, the solution was diluted to the mark with deionized water and mixed well. What is the molarity of the standard Ca2 solution? 2. A 25.00 mL aliquot of the standard calcium solution described in Question 1 was titrated with a previously prepared EDTA solution. In the titration, 32.55 mL of the EDTA solution was required to reach the end point. What is the molarity of the EDTA? 03aS 3. The concentration of Ca2" in an unknown solution was determined by titration with the EDTA solution standardized in Question 2 above. In the determination, 25.00 ml of the unknown solution was diluted to 250.00 mL with deionized water. A 25.00 mL. aliquot of the diluted solution was then titrated with the EDTA solution. The titration required 35.54 mL of the EDTA solution to reach the end point. What is the molarity of calcium in the original unknown solution? oas

Explanation / Answer

1) Molarity =no. of moles of the solute per litre of the solution

0.3412 g of CaCO3 was made upto 500 mL.

Molarity of the solution = 0.3412g/(molecular weight of CaCO3 * volume of solution in litre)

= 0.3412/(100.0869 *0.5000)=0.3412/50.0435 = 0.0068M

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