Question 1
Equal amounts of W and X are mixed and allowed to reach equilibrium.
W + X ⇌ Y + Z
The value of the equilibrium constant is Kc = 4.85. At equilibrium, the mixture will contain
almost all Y and Z
almost all W and X
W, X, Y and Z but there is less Y and Z than W and X
W, X, Y and Z but there is more Y and Z than W and X
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Question 2
One mole of phosphorus(V) chloride, PCl5, is heated to 600 K in a sealed flask of volume 1 dm3.
Equilibrium is established and measurements are taken.
PCl5(g) ⇌ PCl3(g) + Cl2(g)
The experiment is repeated with one mole of phosphorus(V) chloride heated to 600 K in a sealed flask of volume 2 dm3.
How will the measurements vary?
the equilibrium concentrations of PCl3(g) and Cl2(g) are higher in the second experiment
the equilibrium concentration of PCl5(g) is lower in the second experiment
the equilibrium concentrations of all three gases are the same in both experiments
the value of the equilibrium constant is higher in the second experiment
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Question 3
Which statement about the effect of a catalyst on a reversible reaction is correct?
the activation energy of the forward reaction stays the same
the composition of the equilibrium mixture stays the same
the rate of the backward reaction stays the same
the value of the equilibrium constant changes
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Question 4
Chloroethene, CH2=CHCl, is prepared in the presence of a solid catalyst using the equilibrium reaction below.
CH2ClCH2Cl(g) ⇌ CH2=CHCl(g) + HCl(g) ΔH = +51 kJ mol-1
Which change would result in an increased equilibrium yield of chloroethene?
increasing the pressure
increasing the surface area of the catalyst
increasing the temperature
use of a homogeneous catalyst
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Question 5
Hydrogen gas can be produced as shown below.
CH4(g) + H2O(g) ⇌ CO(g) + 3H2(g) ΔH = +206 kJ mol-1
Which conditions produce the greatest equilibrium yield of hydrogen?
low temperature and high pressure
low temperature and low pressure
high temperature and high pressure
high temperature and low pressure
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Question 6
A pale brown mixture of NO2 and N2O4 is allowed to reach equilibrium in a sealed gas syringe according to the following equation.
2NO2(g) ⇌ N2O4(g)
When the plunger is pushed further into the syringe the pressure increases and the mixture becomes paler in colour.
When the syringe is placed in a hot oven the mixture becomes darker in colour.
Which of the following statements is correct?
NO2 is brown and the forward reaction is exothermic
NO2 is brown and the forward reaction is endothermic
NO2 is colourless and the forward reaction is exothermic
NO2 is colourless and the forward reaction is endothermic
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Question 7
Which statement is not always correct for a reaction at equilibrium?
reactants ⇌ products
the concentrations of the reactants and products are equal
the equilibrium can be achieved starting from the reactants
the equilibrium can be achieved starting from the products
the rate of the forward reaction is equal to the rate of the
reverse reaction
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