MYP 10 Chemistry 2013-14
Equilibrium Worksheet 1
Name: _________________________________ ( )
Class: _________ Date: _____________
_________________________________________________________________________________
7.1 Dynamic equilibrium
7.1.1 Outline the characteristics of a chemical and physical systems in a state of equilibrium.
7.2 The position of equilibrium
7.2.1 Deduce the equilibrium constant expression (Kc) from the equation for a homogeneous reaction.
7.2.2 Deduce the extent of a reaction from the magnitude of the equilibrium constant.
7.2.3 Apply Le Chatelier’s principle to predict the qualitative effects of changes of temperature, pressure and concentration on the
position of equilibrium and on the value of the equilibrium constant.
7.2.4 State and explain the effect of a catalyst on an equilibrium reaction.
7.2.5 Apply the concepts of kinetics and equilibrium to industrial processes.
1. Iodine reacts with chlorine to form dark brown iodine monochloride.
I2 + Cl2 → 2ICl
This reacts with more chlorine to give yellow iodine trichloride.
There is an equilibrium between these iodine chlorides.
ICl (l) + Cl2(g)
dark brown
ICl 3(s)
yellow
(a) Explain what is meant by equilibrium.
(b) When the equilibrium mixture is heated it becomes a darker brown colour.
Is the reverse reaction endothermic or exothermic? Give a reason for your choice.
(c) The pressure on the equilibrium mixture is decreased.
(i) How would this affect the position of equilibrium and why?
(ii) Describe what you would observe.
2(a) The diagram below represents equilibrium mixtures for the reaction:
Y + X2
XY + X
at 350K and 550K, respectively. Deduce and explain whether the reaction is exothermic or endothermic.
350 K
550 K
X
Y
(b) The equation for the main reaction in the Haber process is:
N2(g) + 3H2(g)
(i)
2NH3(g)
ΔH= - 92kJmol-1
State two characteristics of a reversible reaction at equilibrium.
(ii) This reaction is described as homogeneous. State what is meant by the term homogeneous.
(iii) Write the equilibrium constant expression for the reaction.
(c) When nitrogen and hydrogen are mixed together at room temperature and atmospheric pressure the
reaction is very slow. In industry, typical values of pressure and temperature used can be 250
atmospheres and 4500C.
(i) State the effects on both the rate of reaction and the value of the equilibrium constant of increasing
the temperature.
(ii) State the effects on both the rate of reaction and the value of the equilibrium constant of increasing
the pressure.
(iii) Suggest why a pressure of 1000 atmosphere is not used.
(iv) State and explain what will happen to the position of the equilibrium if some of the ammonia is
removed.
(d) Name the catalyst used in Haber process. State and explain its effect on the value of the equilibrium
constant.
(e) Use the collision theory to explain the effect of increasing the temperature on the rate of reaction
between nitrogen and hydrogen.
3. For the reversible reaction
H2(g) + I2(g)
2HI(g)
ΔH > 0
the equilibrium constant Kc = 60 at a particular temperature.
(a) Give the equilibrium expression.
(b) For this reaction, what information does the value of Kc provide about the relative concentrations of the
product and reactants at equilibrium.
(c) What effect, if any, will an increase in pressure have on the equilibrium position?
(d) Explain why an increase in temperature increases the value of the equilibrium constant for the above
reaction.
4. The equation for one reversible reaction involving oxides of nitrogen is shown below:
N2O4(g)
NO2 (g)
ΔH= + 57 kJmol-1
Experimental data for this reaction can be represented on the following graph:
(a) Write an equation for the equilibrium constant, Kc, for the reaction. Explain the significance of the
horizontal parts of the lines on the graph. State what can be deduced about the magnitude of Kc for the
reaction, giving a reason.
(b) Use Le Chatelier’s principle to predict and explain the effect of increasing the temperature on the
position of equilibrium.
(c) Use Le Chatelier’s principle to predict and explain the effect of increasing the pressure on the position
of equilibrium.
(d) State and explain the effects of a catalyst on the forward and reverse reactions, on the position of
equilibrium and on the value of Kc.
[SL paper 2, May 05]