In a reversible reaction at equilibrium, how do the rates of the forward and reverse reactions compare?
Equal
Dynamic equilibrium means both reactions continue but occur at the same rate.
What happens to the concentrations of reactants and products at equilibrium?
They remain constant.
Concentrations stay constant because both reactions occur at equal rates, not because reactions stop.
What principle predicts how a system at equilibrium responds to changes in temperature, pressure, or concentration?
Le Chatelier’s principle
It states that a system at equilibrium will oppose a change imposed on it.
Fill in the blank:
If the concentration of a reactant is increased, the equilibrium shifts to _______ the added reactant.
oppose
The system adjusts to reduce the effect of the change by favouring the reaction that consumes the added substance.
True or False:
At equilibrium, the forward and reverse reactions have stopped occurring.
False
Equilibrium is dynamic: both reactions continue but at equal rates.
For a gaseous equilibrium, increasing pressure favours the side with _______ moles of gas.
fewer
The system reduces pressure by shifting toward the side with fewer gas particles.
True or False:
Adding a catalyst changes the position of equilibrium in a reversible reaction.
False
A catalyst speeds up both forward and reverse reactions equally but does not change equilibrium composition.
Why is a compromise temperature often used in industrial equilibrium reactions?
Balance
A compromise balances reaction rate (faster at high temperature) and equilibrium yield (often better at lower temperature).
True or False:
Increasing temperature shifts equilibrium in the endothermic direction.
True
Heat can be treated as a reactant in endothermic reactions, so increasing temperature favours that direction.
Fill in the blank:
If a product is removed from an equilibrium mixture, the equilibrium shifts to produce _______ product.
more
Removing product reduces its concentration, so the system forms more to restore equilibrium.
True or False:
In a homogeneous equilibrium, all reactants and products are in the same physical state.
True
Homogeneous equilibria typically involve all gases or all species dissolved in solution.
Why are high pressures sometimes avoided in industrial equilibrium processes even if they increase yield?
Cost
High pressures require stronger equipment and more energy, increasing economic cost.
For a reversible reaction, how is the equilibrium constant expressed using the concentrations of species?
Products over reactants
Each concentration is raised to the power of its stoichiometric coefficient in the balanced equation.
Fill in the blank:
The concentration of a species used in an equilibrium expression is written using _______ brackets.
square
For example, the concentration of A is written as [A].
What unit is typically used for concentrations in an equilibrium expression for Kc?
mol dm-3
All concentrations used in Kc expressions are measured in mol dm-3.
True or False:
The value of Kc changes if the concentration of reactants or products is altered.
False
Changing concentration shifts the position of equilibrium but does not change the value of Kc.
For the reaction aA + bB ⇌ cC + dD, how are the concentrations of products used in the Kc expression?
Numerator
The expression is Kc = [C]c[D]d / [A]a[B]b.
True or False:
Adding a catalyst changes the value of Kc for a reaction.
False
A catalyst speeds up the attainment of equilibrium but does not alter the equilibrium constant.
What condition must remain constant when calculating or comparing values of Kc?
Temperature
The equilibrium constant only remains constant at a fixed temperature.
Fill in the blank:
If the value of Kc is very large, the equilibrium mixture contains mostly _______.
products
A large Kc indicates the equilibrium position lies far to the right.
True or False:
If Kc is very small, the equilibrium position lies towards the reactants.
True
A small Kc means only a small amount of product is formed at equilibrium.
In a homogeneous equilibrium, in what physical state are all species present?
Same state
Typically all gases or all substances dissolved in the same solution.
What must be known in order to calculate the value of Kc from experimental data?
Equilibrium concentrations
Concentrations must be measured once the system has reached equilibrium.
Fill in the blank:
When calculating Kc, each concentration is raised to the power of its _______ in the balanced equation.
coefficient
The stoichiometric coefficient determines the exponent in the Kc expression.
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3.1.1 Atomic structure50
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3.1.2 Amount of substance47
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3.1.3 Bonding90
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3.1.4 Energetics62
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3.1.5 Kinetics55
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3.1.6 Equilibria & Kc24
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3.1.7 Redox equations17
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3.1.8 Thermodynamics27
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3.1.9 Rate equations24
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3.1.10 Kp12
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3.1.11 Electrode potentials46
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3.1.12 Acids and bases69
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3.2.1 Periodicity22
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3.2.2 Group 2 metals24
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3.2.3 Group 7 (halogens)31
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3.2.4 Period 3 oxides35
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3.2.5 Transition metals95
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3.2.6 Ions in aqueous solution39
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3.3.1 Intro to organic chemistry42
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3.3.2 Alkanes49
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3.3.3 Halogenoalkanes36
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3.3.4 Alkenes36
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3.3.5 Alcohols43
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3.3.6 Organic analysis36
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3.3.7 Optical isomerism12
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3.3.8 Aldehydes & ketones20
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3.3.9 Carboxylic acids & derivatives25
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3.3.10 Aromatic chemistry29
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3.3.11 Amines41
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3.3.12 Polymers24
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3.3.13 Amino acids, proteins, DNA61
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3.3.14 Organic synthesis12
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3.3.15 NMR spectroscopy14
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3.3.16 Chromatography12
