Question

1. Calculate [Ag⁺] for the following electrochemical cell if E_cell = 0.67 V

Pt | H_2(g), (1.00 atm), H⁺ (1.00 M) || Ag⁺ (? M) | Ag

2. How many grams of cadmium are deposited from an aqueous solution of CdSO₄ when an electrical current of 1.15 A flows through the solution for 312 minutes?

3. Write equations for the following nuclear reactions

a) The radioactive decay of nickel-63 by beta emission.

b) The radioactive decay of polonium-207 by alpha emission.

c) The fission reaction of uranium-235 with neutrons to produce xenon-142, rubidium-95 and positron emission.

4. Calculate the binding energy for the beryllium-9 nucleus given its mass is 9.01218 amu.

5. A 50.0 mg sample of pure scandium-44 is extracted from a large quantity of ore. If the half-life of this isotope is 3.43 days, calculate the amount of scandium-44 remaining 12 days after the extraction.

Answer 1

To solve the first question you need the Nernst Equation:

E = 0.67 V

n = 1 (only one electron transfered per atom Ag⁺ --> Ag^o)

F = 96500 (Faraday constant in M.K.S unit system)

T = 298 K (assume ambient temperature since none is given)

R = 8.314472 J.K^-1.mol^-1

E^o = E^o_reduction - E^o_oxidation

In this case the Ag⁺ is reduced to Ag^o, hydrogen H₂ is oxidized to H⁺

E^o = +0.80 V - 0 V (Pt/H₂ is a standard electrode)
E^o = +0.80 V

Q = [H⁺]/[Ag⁺] (H⁺ value, 1)

Then, substitute Q in Nernst Equation and clear [Ag⁺]:

[Ag⁺] = 1/e^{(Eo - E).nF/RT)}

[Ag⁺] = 0.006324 M