31. For each of the to produce 1.00 g of free metal. a. Co b. Hg C. Hg, 32. Answ

Question

31. For each of the to produce 1.00 g of free metal. a. Co b. Hg C. Hg, 32. Answer the following pair of questions. The half-reaction associated with each is the following: Ag (aq) Agls) The mass of silver deposited on a spoon during electroplating was 0.775 mg. How much electrical charge passed though the cell? a. b. What mass of silver could be plated onto a spoon from electrolysis of silver nitrate with a 2.50-A current for 20.0 minutes? 33. What current is needed to deposit 1.75 g of Crls) metal form a solution of C in a period of 20 minutes? An unknown cation of +3 charge was plated out of an aqueous solution. It was determined that 5.71 g of the metal was produced when the current of 4.0 A was applied to the solution for 1.0 hour. Assuming 100% yield, what is the atomic weight of the metal? 34. It took 74.6 seconds for a current of 2.50 A to plate 0.1086 g of a metal from a solution containing M (aq) ions. What is the metal? 35.

Explanation / Answer

Answer 33:

Cr3+ (aq) --------> Cro (s) + 3e-.

Faraday's Law of electrolysis,

m = ITM/Fz

Whrer given data:

m: Mass of a substance liberated in grams = 1.75 g

t: Time for which electricity passed in seconds = 20 min = 1200 s

M: Atomic / molar mass = 52.0 g/mol

F = 96500 C mol?1.

z = Charge on cation or # of electrons transfered

I = Current passed i Ampere.

Using these values in above eq.(1) we get,

1.75 = I*1200*52.00 / 96500*3

I = 1.75*96500*6 / 1200*52.00

I = 8.119 Amp

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