MODULE 2
WORKSHEET
8
EQUILIBRIUM
Syllabus reference 9.3.2
1
Classify each of the following statements as true or false. For the false statements rewrite them so
they are true.
a
For chemical equilibrium to be established the reaction must be irreversible.
FALSE
b
For chemical equilibrium to be established the reaction must be REVERSIBLE.
Dynamic equilibrium occurs when the forward and reverse reactions occur at the same rate.
TRUE
c
Le Chatelier’s principle states that if a system at equilibrium is disturbed the system adjusts
itself to maximise the disturbance.
FALSE
Le Chatelier’s principle states that if a system at equilibrium is disturbed the system
adjusts itself to MINIMISE the disturbance.
d
For a system to be at equilibrium there must be equal amounts of reactants and products.
FALSE
For a system to be at equilibrium there must be equal CHANGES IN THE amounts
of reactants and products.
e
When a system is at equilibrium there are no observable changes in the macroscopic properties.
TRUE
f
CO2(g)  H2O(l) H2CO3(aq) represents the equilibrium equation for carbon dioxide
dissolved in water.
TRUE
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CONQUERINGCHEMISTRY HSC
MODULE 2 WS 8
g
The solubility of CO2 increases as temperature increases.
FALSE
h
The solubility of CO2 increases as temperature DECREASES.
A change in the pressure on a system can cause a shift in the equilibrium position.
TRUE
i
An increase in temperature will cause an exothermic reaction at equilibrium to move to the
left, liberating heat.
FALSE
An increase in temperature will cause an exothermic reaction at equilibrium to move
to the left, ABSORBING heat.
j
Removing the cap on a fizzy drink lowers the CO2 concentration and causes the equilibrium
(CO2(aq) CO2(g)) to move to the left releasing more CO2 gas.
FALSE
Removing the cap on a fizzy drink lowers the CO2 concentration and causes the
equilibrium (CO2(aq)
2
CO2(g)) to move to the RIGHT releasing more CO2 gas.
For the following gaseous reactions, predict the effect upon the position of equilibrium of:
i increasing the pressure (by compressing the equilibrium mixture into a smaller volume)
ii adding H2 to equations b and c
iii adding O2 to equation d and Cl2 to equation a
iv decreasing the temperature
(exothermic)
a SO2(g)  Cl2(g) SO2Cl2(g)
(i) →
(iii) →
(iv) →
b
CO(g)  H2(g)
HCHO(g)
(exothermic)
(i) →
(ii) →
(iv) →
c
CH4(g)  H2O(g)
CO(g)  3H2(g)
(endothermic)
(i) ←
(ii) ←
(iv) ←
d
2SO2(g)  O2(g)
2SO3(g)
(exothermic)
(i) →
(iii) →
(iv) →
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CONQUERINGCHEMISTRY HSC
MODULE 2 WS 8
3
For the reaction:
C(s)  H2O(g)
CO(g)  H2(g)
H  131 kJ/mol
Explain the effect on the equilibrium position of:
a decreasing the volume of the reaction vessel so that the pressures of the individual gases all
increased
Decrease in volume means increase in pressure so system will act to decrease pressure and
reverse reaction will occur at greater rate.
b
increasing the temperature
System will act to decrease temperature so will move in the direction which absorbs heat,
to the right.
c
adding extra solid carbon
Adding solid carbon will not affect the equilibrium.
4
Select the conditions that would maximise the conversion of the underlined reactant to the
underlined product in the following reactions at a fixed temperature.
a
3H2(g)  N2(g)
NH3(g)
Increase pressure
b
4HCl(g)  O2(g)
2Cl2(g)  2H2O(g)
Increase pressure
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CONQUERINGCHEMISTRY HSC
MODULE 2 WS 8
5
The table below shows the solubility of CO2(g) in water in g gas per kg water at a total pressure
of 101.3 kPa.
TEMPERATURE
(°C)
SOLUBILITY
(g/kg H2O)
a
0
20
30
40
60
3.35
1.69
1.26
0.973
0.576
Plot a graph of solubility versus temperature on the grid below.
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CONQUERINGCHEMISTRY HSC
MODULE 2 WS 8
b
Use the graph to determine the solubility of CO2 at 25°C.
Approximately 1.45g/kg H2O
6
Chickens cannot perspire so when they get hot they pant. In hot weather, chickens lay eggs with
thin shells that are easily broken. The following equilibrium system exists:
CO2(g)
CO2(aq)
H2CO3(aq)
H(aq)  HCO3(aq)
HCO3(aq)
H(aq)  CO32(aq)
H2O(l)  CO2(aq)
Overall
CO2(g)
H2CO3(aq)
CO2(aq)
H2CO3(aq)
H  HCO3
H  CO32
Chicken breath
Ca2(aq)  CO32(aq)
CaCO3(s)
egg shell
a
Explain why panting causes weaker egg shells.
Panting means less CO2 gas in system so less CO2(aq). All reactions move to left so less egg
shell produced.
b
To overcome this problem, farmers gave chickens carbonated water. Explain how this can
overcome the problem of weak egg shells.
Carbonated water means increased concentration of CO2(aq) so all reactions move right
producing more egg shell.
Copyright © 2007 McGraw-Hill Australia
CONQUERINGCHEMISTRY HSC
MODULE 2 WS 8