Chem 6c Midterm 1

Chem. 6C Midterm 1
Version A
October 19, 2007
Name__________________________________________
Student Number _________________________________

All work must be shown on the exam for partial credit. Points will be taken off for incorrect or no units. Non graphing calculators and one hand written 3” × 5” note card are allowed.

Problem 1
(of 15 possible)

Problem 2
(of 26 possible)

Problem 3
(of 20 possible)

Problem 4
(of 15 possible)

Problem 5
(of 6 possible)

Problem 6
(of 28 possible)

Problem 7
(of 10 possible)

Problem 8
(of 21 possible)

Problem 9
(of 9 possible)

Midterm Total
(of 150 possible)

I would like my grade to be posted on line by my student number
___________________________________

1

1) Answer the questions below using the following data
Half Reaction
Eº (V)
Ag2+(aq) + e- Ag+(aq)
1.99
1.50
Au3+(aq) + 3e- Au(s)
Fe3+(aq) + e- Fe2+(aq)
0.77
+
2H (aq) + 2e
H2(g)
0.00
Pb2+(aq) + 2e- Pb(s)
-0.126
Ni2+(aq) + 2e- Ni(s)
-0.23
-1.66
Al3+(aq) + 3e- Al(s)
Ca2+(aq) + 2e- Ca(s)
-2.76

(3 pts) Which is the strongest reducing agent?

Ca(s)

(3 pts) Which is the strongest oxidizing agent?

Ag2+(aq)

(3 pts) Will Al(s) dissolve in 1 mol·L-1 HCl?

Yes

(3 pts) Can Pb(s) reduce Ag2+(aq)?

Yes

(3 pts) In the electrochemical cell Ni(s)|Ni2+(aq)||Au3+(aq)|Au(s). What is the emf when the cell is at equilibrium?
At equilibrium the emf = 0 V

2

2) Answer the following questions using the given galvanic cell

MnO4-(aq) + 8H+(aq) + 5e- Mn2+(aq) +4H2O(l)
Cr2O72-(aq) + 14H+(aq) + 6e- 2Cr3+(aq) + 7H2O(l)

Eº = 1.51 V
Eº = 1.33 V

(3 pts) When current is allowed to flow what species is oxidized?
Cr3+
(2 pts) What is the value of Eºcell?
1.51 V – 1.33 V = 0.18 V
(3 pts) What is the oxidation state of Cr in Cr2O72-?
6+
(5 pts) What is the balanced equation of this cell?
6(MnO4-(aq) + 8H+(aq) + 5e- Mn2+(aq) +4H2O(l))
5(2Cr3+(aq) + 7H2O(l) Cr2O72-(aq) + 14H+(aq) + 6e-)