ANSWER E TO J ONLY

A 1.000-g sample containing bromide was dissolved in sufficient water to give 100.0 mL. A 50.00 mL aliquot was measured and after acidification, silver nitrate was introduced to precipitate AgBr, which was filtered, washed, and then dissolved in an ammoniacal solution of potassium tetracyanonickelate(II):

Ni(CN)₄^2- + 2AgBr(s) 2Ag(CN)₂^- + Ni²⁺ + 2Br^-

The liberated nickel ion required 11.70 mL of 0.002146 M EDTA.

a) Write the balanced chemical reaction of Ni²⁺ with EDTA. (2 pts)

b) Calculate mmol Ni in the 50.00 mL aliquot. ( 2 pts)

c) Calculate mmol Br- in the 50.00 mL aliquot. (2 pts)

d) Calculate the percentage of NaBr (102.894) in the 1.000 g sample. (2 pts)

The other 50.00 mL remaining solution was also analyzed for its Br^- content by potentiometry using a metallic electrode of the second kind.

e) Write the cell notation of the potentiometric set-up with SCE as the reference electrode. (2 pts)

f) Write the Nernst equation that describes the indicator electrode set-up. (2 pts)

Ecell recorded in running the solution using the potentiometric set-up was Ecell = 0.0286 V. (E⁰Ag/AgBr = 0.095 V)

g) Compute for Eind. (2 pts)

h) Compute pBr in the 50.00 mL aliquot. (2 pts)

i) Compute for % NaBr ( in the potentiometric technique). (2 pts)

j) Calculate the error between the obtained % NaBr fr the EDTA titration technique and the % NaBr from the potentiometric technique. (1 pt)