CHM 2046
Quiz 3B
March 31, 2006
Answer all questions.
Look at the end for useful information.
1.
Consider the two reactions below.
Mg (s) + ½O
2
(g)
→
MgO (s)
∆
G° =  569 kJ
2CO
2
(g)
→
2CO (g) + O
2
(g)
∆
G° = + 514 kJ
a)
(4 points)
What is the resulting reaction obtained from coupling the above
reactions together (no O
2
(g) should appear)?
Multiply the first by 2, or divide the second by ½, and add together
2 Mg (s) + 2 CO
2
(g)
→
2 MgO (s) + 2 CO (g)
or Mg (s) + CO
2
(g)
→
MgO (s) + CO (g)
b)
(4 points)
What is
∆
G° for the reaction in part a)?
Multiply the second
∆
G°
by 2, or divide the first by ½, and add together
For 2 Mg (s) + 2 CO
2
(g)
→
2 MgO (s) + 2 CO (g)
∆
G° = 1138 kJ + 514 kJ = 624 kJ
For Mg (s) + CO
2
(g)
→
MgO (s) + CO (g)
∆
G° =  569 kJ + 257 kJ = 312 kJ
2.
The reaction below at 298 K has an equilibrium constant of 3.89 x 10
34
.
2 HCl (g)
⇌
H
2
(g) + Cl
2
(g)
a)
(2 points)
Does the equilibrium lie far to the left, far to the right, or
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 Spring '07
 veige/martin
 Chemistry, Reaction, Redox

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