2 questions: full credit for both questions. 1. The electrolysis of any aqueious

Question

2 questions: full credit for both questions.

1. The electrolysis of any aqueious solutioin requires the presence of of an electrolyte to carry the current in solution. If you wanted to electrolyze water in order to produce H2 (g) at the cathode and O2 at the anode, which electrolyte would be most appropriate?

a. LiBr b. PbCl2 c. MgF2 d a,b,or c e. none of these

2. what current is required to electroplate a layer of solid nickel from a solution of NiSO4 (aq) at a rate of 0.125 g/min?

A. 2.69 A

B. 3.42 A

C. 4.88 A

D. 1.71 A

E. 6.85 A

Explanation / Answer

1) a. LiBr

2) 0.125 g Ni/min / 58.7 g/mol = 2.13 X 10^-3 mol/min / 60 s/min = 3.55 X 10^-5 mol/s

Since you are plating Ni2+ --> Ni(s), you need 2 moles of electrons for each mole of Ni(s) plated. So,

moles electrons = 3.55X10^-5 X 2 = 7.10 X 10^-5 mol electrons

Number of coulombs = moles electrons X 96485 C/mol e-
Coulombs = 7.10 X 10^-5 X 96485 = 6.85 Coulomb

Coulombs = amperes X seconds
6.85 = amperes X 1 s = 6.84 amp current

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