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Titrations Lecture 2, Oct 11. Homework Ch 5 Problems 3,4,6,9,12,13,14 Due Wed Oct 16.

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Presentation on theme: "Titrations Lecture 2, Oct 11. Homework Ch 5 Problems 3,4,6,9,12,13,14 Due Wed Oct 16."— Presentation transcript:

1 Titrations Lecture 2, Oct 11

2 Homework Ch 5 Problems 3,4,6,9,12,13,14 Due Wed Oct 16

3 Calculations for Titrations In a back titration, the calculation consists of 1)Calculation of the total number of moles of the excess reactant. 2)From the titration with the second reactant, calculate the number of moles of analyte that has reacted with the first reactant.

4 Although most of the metallic ions of the periodic table can be determined with edta, several require a back titration because of slow kinetics or an unsuitable indicator.

5 Problem 1 - A mL aliquot of a solution of Hg +2 was adjusted to a pH of 10.0 with ammonia and treated with mL of M edta. The excess edta required mL of M Mg +2 to reach the Eriochrome black T end point. What is the conc of Hg +2 in the original solution?

6 Edta reacts 1:1 with all metals through the first 2 transition series. # mmol of edta = 10.00mL x M = mmol

7 Problem 1 - A mL aliquot of a solution of Hg +2 was adjusted to a pH of 10.0 with ammonia and treated with mL of M edta. The excess edta required mL of M Mg +2 to reach the Eriochrome black T end point. What is the conc of Hg +2 in the original solution? Edta reacts 1:1 with all metals through the first 2 transition series. # mmol of edta = 10.00mL x M = mmol # mmol Mg +2 = 24.66mL x = mmol

8 Problem 1 - A mL aliquot of a solution of Hg +2 was adjusted to a pH of 10.0 with ammonia and treated with mL of M edta. The excess edta required mL of M Mg +2 to reach the Eriochrome black T end point. What is the conc of Hg +2 in the original solution? Edta reacts 1:1 with all metals through the first 2 transition series. # mmol of edta = 10.00mL x M = mmol # mmol Mg +2 = 24.66mL x = mmol # mmol difference = # mmol Hg +2 = mmol

9 Problem 1 - A mL aliquot of a solution of Hg +2 was adjusted to a pH of 10.0 with ammonia and treated with mL of M edta. The excess edta required mL of M Mg +2 to reach the Eriochrome black T end point. What is the conc of Hg +2 in the original solution? Edta reacts 1:1 with all metals through the first 2 transition series. # mmol of edta = 10.00mL x M = mmol mmol Mg +2 = 24.66mL x = mmol # mmol difference = # mmol Hg +2 = mmol Conc Hg +2 = mmol/25.00 mL = x M

10 Problem 1 - A mL aliquot of a solution of Hg +2 was adjusted to a pH of 10.0 with ammonia and treated with mL of M edta. The excess edta required mL of M Mg +2 to reach the Eriochrome black T end point. What is the conc of Hg +2 in the original solution? Edta reacts 1:1 with all metals through the first 2 transition series. # mmol of edta = 10.00mL x M = mmol mmol Mg +2 = 24.66mL x = mmol # mmol difference = # mmol Hg +2 = mmol Conc Hg +2 = mmol/25.00 mL = x M Mass of Hg +2 per L = x x g/mol = g/L

11 Problem 2 - The purity of ethyl acetate was determined by treatment of a g sample with mL of M KOH and heating to saponify the ester. (products are ethyl alcohol and acetic acid). The excess KOH required mL of M HCl to reach the equivalence point. What is the purity of the ester?

12 # mmol KOH = 75.00mL x M = mmol

13 Problem 2 - The purity of ethyl acetate was determined by treatment of a g sample with mL of M KOH and heating to saponify the ester. (products are ethyl alcohol and acetic acid). The excess KOH required mL of M HCl to reach the equivalence point. What is the purity of the ester? # mmol KOH = 75.00mL x M = mmol #mmol HCl = 32.53mL x M = mmol

14 Problem 2 - The purity of ethyl acetate was determined by treatment of a g sample with mL of M KOH and heating to saponify the ester. (products are ethyl alcohol and acetic acid). The excess KOH required mL of M HCl to reach the equivalence point. What is the purity of the ester? # mmol KOH = 75.00mL x M = mmol #mmol HCl = 32.53mL x M = mmol diff = # mmol HAc = mmol

15 Problem 2 - The purity of ethyl acetate was determined by treatment of a g sample with mL of M KOH and heating to saponify the ester. (products are ethyl alcohol and acetic acid). The excess KOH required mL of M HCl to reach the equivalence point. What is the purity of the ester? # mmol KOH = 75.00mL x M = mmol #mmol HCl = 32.53mL x M = mmol diff = # mmol HAc = mmol MM ethylacetate = MM g/mol

16 Problem 2 - The purity of ethyl acetate was determined by treatment of a g sample with mL of M KOH and heating to saponify the ester. (products are ethyl alcohol and acetic acid). The excess KOH required mL of M HCl to reach the equivalence point. What is the purity of the ester? # mmol KOH = 75.00mL x M = mmol #mmol HCl = 32.53mL x M = mmol diff = # mmol HAc = mmol MM ethylacetate = MM g/mol Mass of ethylacetate = x mol x g/mol = g

17 Problem 2 - The purity of ethyl acetate was determined by treatment of a g sample with mL of M KOH and heating to saponify the ester. (products are ethyl alcohol and acetic acid). The excess KOH required mL of M HCl to reach the equivalence point. What is the purity of the ester? # mmol KOH = 75.00mL x M = mmol #mmol HCl = 32.53mL x M = mmol diff = # mmol HAc = mmol MM ethylacetate = MM g/mol Mass of ethylacetate = x mol x g/mol = g % purity = x 100 / = % pure


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