Question

Hi, I do have all the correct answers for these questions, but I want to know why it's correct/incorrect

Please response with detail reasons. Thank you

1) Which of the following is incorrect about chemical indicators used in precipitation titration?

a. Chromate is the indicator used in the Mohr method.

b. In the titration of Cl- with Ag+ ion using the Fajans method, the color change occurring at the end point is attributed to the absorption of fluorescein anion into the AgCl precipitate.

c. In the determination of Cl- by Ag+ -based back titration using the Volhard method, the color change occurring at the end point is from light yellow to bright red.

d. In a titration of Cl- with Ag+ ion as titrant with the Mohr method, the color change at the end point is yellow to bright red.

Given the information in the above question, which of the following argument is NOT correct?

a. Electrons move from the Zn electrode to the Cu electrode through a metal wire.

b. The reaction occurs on the Zn electrode is: Zn Æ Zn2+ + 2e

c. The chloride ion in the salt bridge moves to the container bearing the Cu electrode.

d. As time moves along, the weight of the Cu electrode will increase.

14. How many pairs of electrons can H2O, N(CH2COO- )3, and EDTA donate when they form complexes with metal?

a. 1, 2, 6

b. 1, 4, 6

c. 2, 4, 12

d. 2, 8, 12

Answer 1

Ans-1) if the solution contain dichlorofluorescein anion ,some of this wil get adsorbed onto the Ag+ ion present on the precipitate surface and form red colour silver dichlorofluorescein.however adsorption of Ag+ on the silver chloride precipitate increases the concentration of Ag+ which is capable of precipitating red silver fluorescein.Hence this dichlorofluorescein behaves as a absorption indicator.

Ans2-) negatively charged species in the salt bridge moves to anodeichaldf cell.hence it moves to Zn not Cu.

Ans-3) H2O has one lone pair on Oxygen.N+CH2COO-)3 has 4 electrons pair.3 on oxygen and one on nitrogen. EDTA is hexadented ligand.