0.2 moles of A, 0.06 moles of B, 0.0125 moles of C and 0.5 moles of D are mixed together and allowed to attain equilibrium. If Kc for the reaction is 4 calculate the equilibrium concentration of the resulting mixture
Answers
Answer:
First set balance the equation
2
A
+
2
B
=
2
A
B
2. Now write the equilibrium constant for the reaction
K
c
=
[
A
B
]
[
A
]
[
B
]
3. As
K
c
is being determined the temperature matters and thus volume also matters.So the conversion of moles to molarity is necessary
M
=
moles
L
4. As the volume of the container is
2dm
3
Conversionof
d
m
3
to litres is necessary
1
d
m
3
=
1
L
∴
2
d
m
3
=
2
L
5. Calculate the molarities
Conc. of A =
0.2moles
2
L
=
0.1
M
Conc. of B =
0.4mole
2
L
=
0.2
M
Conc. of A at equilibrium
0.1moles
2
L
=
0.05
M
5. Set up an ICE table
For problems related to equilibrium
concentrations,you need to set up an ICE table.
m
m
m
m
m
l
2A
l
m
+
m
m
m
m
2B
l
l
l
l
→
m
l
2
A
B
I/mol:
m
l
l
0.1
M
m
m
m
m
m
l
0.2
M
m
m
m
m
m
l
0
C/mol:
m
−
x
m
m
m
m
m
m
−
x
m
m
m
m
+
2
x
E/mol:
l
m
0.1
M
−
x
m
m
l
0.2
M
−
x
l
m
m
m
l
2
x
From the given information we know that the equilibrium amount of A is 0.05M. Thus
0.1
M
−
x
=
0.05
M
Solve for
x
0.1
M
−
x
=
0.05
M
x
=
0.1
M
−
0.05
M
x
=
0.05
M
6. Solve for the equilibrium amounts of B and AB
A
B
=
2
x
=
2
×
0.05
M
=
0.1
M
B
=
0.2
M
−
0.05
M
=
0.15
M
And we know the equilibrium amounts of A
7. Now solve for
K
c
K
c
=
products
reactants
K
c
=
[
0.1
M
]
[
0.05
M
]
[
0.15
M
]
K
c
=
13.333
If you want
three sig figs
K
c
=
13.4
You can also calculate the
Q
c
to see to which direction will the reaction proceed
Q
c
=
[
A
B
]
2
[
A
]
2
[
B
]
2
Q
c
=
177.777777778
As
K
c
<
Q
c
Reaction will proceed towards left