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WorksheetsLe Chatelier's principle
Total questions: 23
Worksheet time: 12mins
Which of the following is true with regards to a catalyst for the following reaction
A + B ⇋ C + D ∆H = negative
A catalyst will decrease the enthalpy change of the reaction
A catalyst will alter the composition of the equilibrium mixture
A catalyst increases the rate of effective collision
A catalyst does not take part in the reaction
In which of the following systems, does the product yield increase with increasing pressure at constant temperature?
H2 (g) + I2 (g) ⇋ 2 HI (g)
2 HI (g) + S (s) ⇋ H2S (s) + I2 (g)
CaCO3 (s) ⇋ CaO (s) + CO2 (g)
PCl3 (g) + Cl2 (g) ⇋ PCl5 (g)
The reforming of methane is the principal commercial source of hydrogen gas. The equation for the endothermic reaction involved is as follows:
CH4 (g) + H2O (g) ⇋ CO (g) + 3 H2 (g)
At equilibrium, the quantity of hydrogen gas formed can be increased by
Adding a suitable catalyst
Increasing the temperature
Adding a dehydrating agent
Reducing the volume of the vessel
This reaction may be endothermic, exothermic or thermoneutral. Which statement is true of the reaction?
The concentration of c increases with temperature.
The number of moles of A, B and C are the same at equilibrium.
The values of the rate constants k1 and k-1 increase when a catalyst is added.
The activation energy for the forward reaction is lower than that of the reverse reaction.
The reaction equation of the dissociation of HI is shown below.
2 HI (g) ⇋ H2 (g) + I2 (g)
An experiment is accrued out to determine the thermal stability of HI. It is found that it dissociates completely at high temperature and the degree of dissociation increases with temperature. What can be deduced from the experiment?
The H-I bond is strong.
The reaction is endothermic.
The activation energy is lower at high temperature.
Kp does not change with temperature.
The equation of a Haber process is shown below.
N2 (g) + 3 H2 (g) ⇋ 2 NH3 (g) ∆H = -92 kJ
A high yield of ammonia is obtained by
Increasing the temperature to above 900 ˚C
Increasing the pressure to above 200 atm.
Adding argon at constant volume.
Using iron filling.
The equilibrium system of the decomposition of carbon dioxide to carbon monoxide and oxygen is shown in the equation below.
2 CO2 (g) ⇋ 2 CO (g) + O2 (g) ∆H = +566 kJ
Which of the following increases the value of equilibrium constant, Kp, of the system?
reducing the pressure
increasing the temperature
increasing the volume of carbon dioxide
addition of catalyst
1. The formation of SO3 is shown in the equilibrium equation below.
k1
2 SO2 (g) + O2 (g) ⇋ 2 SO3 (g)
k2
Which are the effects of a catalyst on the reaction?
k1 increases, Kc and concentration of SO3 not change
k1 increases, Kc and concentration of SO3 decrease
k1 decreases, Kc unchanged, concentration of SO3 decreases
k1 decreases, Kc and concentration of SO3 increases
In which of the following is the equilibrium position not affected by a change in pressure?
2 SO2 (g) + O2 (g) ⇋ 2 SO3 (g)
H2 (g) + Br2 (g) ⇋ 2 HBr (g)
2 NH3 (g) ⇋ 3 H2 (g) + N2 (g)
CO (g) + 2 H2 (g) ⇋ CH3OH (g)
The following equation represents the decomposition of hydrazine to its elements.
N2H4 (g) ⇋ N2 (g) + 2 H2 (g) ∆H = -95.4 kJ
Which of the following statements is true?
More hydrogen gas will be obtained if a suitable catalyst is used.
More nitrogen can be obtained by compressing the mixture.
More hydrazine will dissociate if a lower temperature is used.
The equilibrium constant Kc will decrease if a higher pressure is used.
A flask contains an equilibrium mixture of sulphur dioxide gas, oxygen gas and sulphut trioxide gas at temperature T.
2 SO2 (g) + O2 (g) ⇋ 2 SO3 (g)
Which of the following will happen if the volume of the flask is suddenly decreased at constant temperature?
The reaction rate will decrease.
The concentration of sulphur dioxide gas will increase.
The number of moles of sulphur trioxide gas will increase.
The equilibrium constant Kp will decrease.
1. For the reaction, 2 XY2 (g) ⇋ X2 (g) + 2 Y2 (g), the numerical value of Kp at different temperature is as follows:
8.91 x 10-5 at 300 K and 5.11 x 10-3 at 540 K
Which of the following statements is correct?
More XY2 will dissociate at a higher pressure.
The unit of Kp of the reverse reaction is atm2.
The decomposition of XY2 is an exothermic reaction.
A high temperature favours the decomposition of XY2.
The effect of pressure on the amount of products is represented in the following graph. Which of the following equation is correctly represented by the graph?
A (g) ⇋ C (g) + D (g)
2 A (g) + B (g) ⇋ C (g)
2 A (g) ⇋ B (g) + C (g)
A (g) + 2 B (g) ⇋ C (g) + 2 D (g)
The effect of volume on the amount of products is represented in the following graph. Which of the following equation is correctly represented by the graph?
N2 (g) + 3 H2 (g) ⇋ 2 NH3 (g)
PCl5 (g) ⇋ PCl3 (g) + Cl2 (g)
2 SO2 (g) + O2 (g) ⇋ 2 SO3 (g)
2 COF2 (g) ⇋ CO2 (g) + CF4 (g)
Which statement about the activation energy of an endothermic reaction is true?
The activation energy of the reaction varies with temperature.
The rate of the reaction is higher if the activation energy of the reaction is larger.
The presence of a catalyst has no effect on the activation energy of the reaction.
The activation energy for the forward reaction is larger than that of the backward reaction
Which of the following reaction will show the graph above?
H2 (g) + Br2 (g) ⇋ 2 HBr (g)
N2 (g) + 3 H2 (g) ⇋ 2 NH3 (g)
CaCO3 (s) ⇋ CaO (s) + CO2 (g)
N2O4 (g) ⇋ 2 NO2 (g)
N2O4 (g) ⇋ 2 NO2 (g) ∆H = positive
Which of the following will increase the Kc of the above equilibrium?
Addition of a suitable catalyst
Increasing the temperature
Increasing the partial pressure of N2O4
Decreasing the activation energy for the forward reaction
CaCO3 (s) ⇋ CaO (s) + CO2 (g)
The Kp for the above reaction is 320 kPa at 298 K and 1.8 x 105 kPa at 6000 K. It can be concluded that
Increase of pressure will increase the yield of carbon dioxide
Forward reaction is endothermic.
The addition of solid calcium oxide will increase the amount of carbon dioxide.
The Kp depends on the amount of calcium carbonate used.
The Kc values for a reaction increases with increasing temperature. Which of the following statements are true for the reaction?
I the reverse reaction is exothermic
II the amount of products increase with the increase of temperature
III the equilibrium position will shift to the right when pressure increases
I only
III only
I and II
II and III
Which of the following factors will affect the position of equilibrium of a reversible reaction?
I temperature
II concentration
III catalyst
I only
I and II
II and III
I, II and III
For a system at equilibrium, the presence of a catalyst will
Increase the equilibrium constant
Increase the rate constant for the forward reaction but not the rate constant for the reverse reaction
Increase the speed of reacting particles
Cause the reaction to proceed by an alternative route
1. NO is produced in internal combustion engines and from lightning according to the following equation:
N2 (g) + O2 (g) ⇋ 2 NO (g) ∆H = positive
Which statement is true about the production of NO?
The reaction of formation of NO releases heat.
High pressure in the engine promotes the formation of NO.
High temperature due to petrol combustion in the engine promotes the production of NO.
High concentration of nitrogen and oxygen are due lightning discharges which promote the production of NO.
Which of the following equilibrium reactions will shift to the right if the pressure is increased at a fixed temperature?
PCl5 (g) ⇋ PCl3 (g) + Cl2 (g)
O2 (g) + 2 F2 (g) ⇋ 2 F2O 9g)
C5H12 (g) + 8 O2 (g) ⇋ 5 CO2 (g) + 6 H2O (g)
3 Fe (s) + 4 H2O (g) ⇋ Fe3O4 (s) + 4 H2 (g)
