Consider the reaction shown below. CA pts) 1) which element is reduced in the re

Question

Consider the reaction shown below. CA pts) 1) which element is reduced in the reaction? D) o E) C C4 pts) 2) Which element is oxidized in the reaction? A Fe B) N C) O D) H E) S Calculate the number of grams of aluminum produced in 1o.o minutes by electrolysis of AICI 3 at a current of 7.0 A. (4 pts) 4) The standard emf for the cell using the overall cell reaction below is +0.154 V: Pb2 (ag) Ni (s) Pb (s) Ni' (aq) What is the emf generated by the cell when [Ni 1-0.75 M and [Pb 1 025 Mis v (4 pts) A) 1.52 B) 2.08 C) 0.04 D) 0.14 E) 0.19 What is the oxidation number of bromine in the bromate (CIO31)ion? (4 pts) A) 22 B) +5 C) +3 D) -3 E)-1 (A pts 6) Balance the following redox reaction occurring in acidic solution.

Explanation / Answer

Question 1.

3H2S + 2H+ + 2NO3- --> 3S(s) + 2NO(g) + 4H2O(l)

a)

element being reduced?

It must be the species GAINING electrons, so

N goes from +5 in NO3- to +2 in NO2, it gains 3 electrons

this is REDUCING

b)

the species being oxidized is

S, since

it goes form -2 in H2S, to 0 in S(s)

so it loses 2 electrons

c)

the numebr of Aluminium produced in t = 10 mins = 10*60 = 600 seconds in electrolysis at I = 7 A = 7 C/s

total charge:

C = I*t = 600*7 = 4200 C

1 mol of e- = 96500 C

x mol of e- =  4200 C

mol of e- = 4200/96500 = 0.0435 mol of e-

1 mol of Al+3 requires 3 mol fo e-

so

0.0435 mol of e- --> 1/3*0.0435 = 0.0145 mol of Al

mass = mol*MW = 0.0145*26.99 = 0.391355 g of Al produced

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