Question

# 1. The standard reduction potential for the reduction of Eu3+(aq) to Eu2+(aq) is -0.43 V. Using...

1. The standard reduction potential for the reduction of Eu3+(aq) to Eu2+(aq) is -0.43 V. Using Appendix E in the textbook, which of the following substances is capable of reducing Eu3+(aq) to Eu2+(aq) under standard conditions?

a. Al

B. Co

C. H2O

D. N2H5

E. H2C2O4

2. How many minutes will it take to plate out 4.56 g of Ni metal from a solution of Ni2+ using a current of 40.5 amps in an electrolytic cell?

3. Using the standard reduction potentials listed in Appendix E in the textbook, calculate the equilibrium constant for each of the following reactions at 298 K.

A. Cu(s)+2Ag+(aq)→Cu2+(aq)+2Ag(s) --Express the equilibrium constant to two significant digits.

B. 3Ce4+(aq)+Bi(s)+H2O(l)→3Ce3+(aq)+BiO+(aq)+2H+(aq)

C. N2H5+(aq)+4Fe(CN)63−(aq)→N2(g)+5H+(aq)+4Fe(CN)64−(aq)

Ans.1

When the standard reduction potential is less than the -0.43 V then it can reduce the Eu3+ to Eu2+

Al = -1.66 V = Yes

Co = 1.82 V = No

H2O2 = 1.78 V = No

N2H5+ = -0.23 V = No

H2C2O4 = -0.49 V = Yes.

Ans 2.

The amount of Ni plated out = 4.56 g

Equivalent weight of Ni = 58.69 /2 = 29.35

number of equivalents of Ni = Mass / Equivalent weight = 4.56 / 29.35 = 0.155

The charge required for 1 gram equivalent = 96500 Coloumbs

So for 0.155 g equ = 96500 X 0.155 = 14957.5 C

current = 40.5amp

time = charge / Current = 14957.5 / 40.5= 369.32seconds

time in minutes = 369.32/ 60 = 6.56 minutes appr.

Ans 3.

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