CHEM 130 Name _____________________________________________
Quiz 9 – November 17, 2017
Complete the following problems. Write your final answers in the blanks provided.
1. At 25
o
C, 0.760 mol SO
3
is placed in an otherwise empty 5.00 L container. When equilibrium is
reached, 0.160 mol of O
2
is present. What is K
c
at this temperature? (8 pts)
2SO
3
(g) 2SO
2
(g) + O
2
(g)
There are several ways to approach this. In the end, we need equilibrium concentrations of all
species.
2SO
3
2SO
2
+
O
2
I 0.760 mol/5 L = 0.152 M 0 0
C
-2x +2x +x
E
0.152-2(0.032) =0.088 M
0+2(0.032) =0.064 M
0.160 mol/5L =
0.
0
320 M
=x
K
c
=
[SO
2
]
2
[O
2
]
=
(0.0640)
2
(0.0320)
=
0.0169
[SO
3
]
2
(0.088)
2
Answer_______0.0169________________
2. Determine K
c
for the reaction: 2NOCl(g) N
2
(g) + O
2
(g) + Cl
2
(g) from the following data at 298K:
(8 points) ½ N
2
(g) + O
2
(g) NO
2
(g) K
c
= 1.0 x 10
-
9
NOCl(g) + ½ O
2
(g) NO
2
Cl(g) K
c
= 1.1 x 10
2
NO
2
(g) + ½ Cl
2
(g) NO
2
Cl(g) K
c
= 0.3
We need to rearrange reactions to make our target reaction:
2(NO
2
(g) ½ N
2
(g) + O
2
(g)) K
c
= 1/(1.0 x 10
-
9
)
2
2(NOCl(g) + ½ O
2
(g) NO
2
Cl(g)) K
c
= (1.1 x 10
2
)
2
2(NO
2
Cl(g) NO
2
(g) + ½ Cl
2
(g)) K
c
= 1/(0.3)
2
So, the sum of the reactions is:
2NO
2
+ 2NOCl + O
2
+ 2NO
2
Cl N
2
+ 2O
2
+ 2NO
2
Cl + 2NO
2
+ Cl
2
2NO
2
Cl N
2
+ O
2
+ Cl
2
K
c
=
(1.1 x 10
2
)
2
=
1.3 x10
23
(1.0 x 10
-
9
)
2
(0.3)
2
Answer______1.3 x10
23
_________________
