hmwrk 10.docx - Thomas Edison State University General...

Thomas Edison State University
General Chemistry II with Labs (CHE-122)
Section no.:
Semester and year: Spring 2019
Written Assignment 10: Electrochemistry
Answer all assigned questions and problems, and show all work.
1. Balance the following redox equations by the ion-electron method:
(25 points)
a. H
2
O
2
+ Fe
+2
→ Fe
+3
+ H
2
O (in acidic solution)
2Fe
+2
+ H
2
O
2
+ 2H + → 2Fe
+3
+ 2H
2
O
b. Cu + HNO
3
→ Cu
+2
+ NO + H
2
O (in acidic solution)
3Cu + 2HNO
3
6H
+
→ 3Cu
+2
+ 2NO + 4H
2
O
c. CN
–
+ MnO
4
–
→ CNO
–
+ MnO
2
(in basic solution)
3CN
–
+ 2MnO
4
H
2
O→ 3CNO
–
+ 2MnO
2
+ 2OH-
d. Br
2
→ BrO
3
–
+ Br
–
(in basic solution)
3Br
2
+2OH- → BrO
3
+ 5Br
–
+ 2H
2
O
e. S
2
O
3
–2
+ I
2
→ I
–
+ S
4
O
6
2–
(in acidic solution)
2S
2
O
3
–2
+ I
2
→ 2 I
–
+ S
4
O
6
2–
(Reference: Chang 18.1)
2. Calculate the standard emf of a cell that uses the Mg/Mg
+2
and Cu/Cu
+2
half-cell reactions
at 25ºC. Write the equation for the cell reaction that occurs under standard-state
conditions. (10 points)