1. The reaction between SO2 and O2 may be described as
2SO2(g) + O2(g) 2SO3(g) ΔH = -196 kJ mol-1
Select the two conditions that will favour a high yield of SO3.
A Removal of SO2
B Lower the pressure
C Lower the temperature
D Use a catalyst
E Addition of more O2
2. A chemical reaction has reached dynamic equilibrium at a certain temperature. Which one of following statements is incorrect?
A The reaction has stopped completely
B The concentrations of the reactants remains constant
C Products are continuously being formed
D The rate of the forward reaction is equal to the rate of the reverse reaction
3. Three moles of ethanol and three moles of ethanoic acid were reacted together according to the equation
C2H5OH + CH3COOH CH3COOC2H5 + H2O
At equilibrium, there was 2 moles each of ethyl ethanoate and water formed. What is the equilibrium constant for this reaction?
A 4
B 2
C 0.25
D 0.44
4. In which of the following would a change in pressure not affect the yield of product
5. A catalyst is added to a chemical reaction at equilibrium. Which statement about catalysts is correct?
6. Nitrogen dioxide can be produced in a number of ways but industrially it is produced using the Ostwald process. Inthe first stage of this process nitrogen monoxide is produced by passing over a hot catalyst.
In the second stage of this process the nitrogen monoxide combines with oxygen in an exothermic reaction to produce nitrogen dioxide.
What happens to the yield of nitrogen dioxide if the reaction mixture in stage 2 is cooled?
7. One method used to produce methanol requires synthesis gas. The following equation shows the production of methanol from synthesis gas.
Which line in the table shows the conditions that would cause the greatest increase in the amount of methanol produced?
8. If the yield of ammonia at equilibrium is 15% then the equilibrium position lies…
A well to the right
B well to the left
C almost centrally
D equally to each side
9. Equilibrium is reached when the rate of the forward reaction…………
A reaches zero
B reaches its minimum
C equals the back reaction rate
D is twice the back reactionrate
10. If the equilibrium position for a reaction lies well to the right, then the equilibrium mixture will contain…
A more products than reactants
B more reactants than products
C only reactants
D only products
11. Starting with NH3 rather than N2 and H2 , would give an equilibrium mixture with..
A a greater proportion of ammonia
B less nitrogen
C the same proportions of all three gases
D less ammonia than before
12. Which conditions would give the best yield of Hydrogen at equilibrium in this reaction?
CH4(g) + HO(g)↔CO(g) + 3H2(g) Δ= +210kJ
A High temperature and low pressure
B High temperature and high pressure
C Low temperature and low pressure
D Low temperature and high pressure
13. In which reaction below will a change in pressure have no effect on the composition of the equilibrium mixture?
A 4NH3(g) + 5O2(g) ↔ 4NO2(g) + 6H2O(l)
B 2SO2 (g) + O2(g) ↔ 2SO3(g)
C CO(g) + H2O(g) ↔ CO2(g) + H2O(g)
D C2H4(g) + H2O(g) ↔ C2H5OH(g)
14. Ammonia gas dissolves in water to form an alkaline solution.
NH3(g) + H2O(l) ↔ NH4 + (aq) + OH– (aq) ΔH = -31kJ
How would each of the following changes affect the position of equilibrium?
a) Increasing the temperature.
b) Increasing the pressure.
c) Adding ammonium chloride.
15. The diagram shows the concentrations of hydrogen, iodine and hydrogen iodide for the reaction between hydrogen and iodine.
Which of the following statements is incorrect?
A the equilibrium lies predominantly to the left
B at point A on the time axis, the concentration of all three gases is zero
C The reaction between the gases reaches equilibrium at point B.
D Adding more hydrogen at point D will alter the shape of the graph.
E At point C, the system is in a state of dynamic equilibrium.
16. Consider the following equilibrium reaction
Which one of the following will cause a yellow colour to predominate?
A Addition of sodium hydroxide (NaOH)
B Addition of sodium chromate (Na2CrO4)
C Addition of hydrochloric acid (HCl)
D Removal of water
17. Which one of the following equilibrium reactions is not affected by a change in pressure?
A
B
C
D
18. What does it mean to say that a chemical reaction has reached equilibrium?
19. The forward reaction of the equilibrium system below is endothermic. Dilute HCl is added and the colour changes to blue. What colour change occurs when the mixture is cooled?
20. The reaction of nitrogen dioxide (NO2) forming dinitrogen tetroxide (N2O4) is exothermic in the forward direction.
State two conditions will cause the equilibrium mixture to go dark brown?
21. Ammonia is formed in the Haber process according to the following balanced equation.
N2 + 3H2 2NH3
The table shows the percentages of ammonia present at equilibrium under different conditions of temperature T and pressure P when hydrogen and nitrogen gases were mixed in a 3:1 molar ratio. Is this an endothermic or exothermic reaction? Give a reason for your answer.
22. The following equilibrium involves two compounds of phosphorus.
PCl3(g) + 3NH3 (g) P(NH2)3(g) + 3HCl(g)
(a) An increase in temperature moves the equilibrium to the left. What does this indicate about the enthalpy change for the forward reaction?
(b) What effect, if any, will an increase in pressure have on the equilibrium?
23. The balanced equation for a reaction at equilibrium is:
aA + bB cC + dD
(a) For this reaction, the equilibrium constant, K, can be defined as:
where [A] represents the concentration of A, etc and a represents the number of moles of A,etc.
(i) Write down the expression for the equilibrium constant for the following equilibrium.
N2(g) + 3H2(g) 2NH3(g)
(ii) What will happen to the position of the equilibrium if the reaction is carried out over a catalyst?
(b) In industry, the reaction of nitrogen with hydrogen to produce ammonia by the Haber Process does not attain equilibrium.
Give one feature of the operating conditions which leads to the Haber Process not reaching equilibrium
24. When a yellow solution of iron (III) chloride (FeCl3)and a colourless solution of potassium thiocyanate (KCNS) were mixed in a test tube, a red colour appeared and the following equilibrium was established:
Fe3+(aq) + CNS–(aq) Fe(CNS)2+(aq)
yellow red
Explain:
(a) the effect on the Fe3+ ion concentration of adding KCNS to the equilibrium mixture
(b) why changing the pressure has no effect on this reaction.
25. Consider the following equilibrium reaction at room temperature used to dissolve iodine (I2) crystals in an aqueous solution of iodide ions (I–).
I2(aq) + I –(aq) I3–(aq)
State and explain the effect on the equilibrium concentration of triiodide ions of adding a substance that reacts with iodine, eg. starch.
26. Iodine monochloride and chlorine gas react together to establish the following equilibrium in a closed system.
Which line in the table shows the conditions that would cause the greatest increase in the amount of ICl3 produced in this reaction.
