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Define the term dynamic equilibrium.
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Define the term dynamic equilibrium.
Dynamic equilibrium is where the rate of the forward reaction equals the rate of the reverse reaction, and the concentrations of reactants and products remain constant.
Define the term closed system.
A closed system is a system where none of the reactants or products can enter or leave the reaction vessel.
Define the term open system.
An open system is a system where the reactants or products can both enter or leave the reaction vessel.
True or False?
Equilibrium can only be reached in a closed system.
True.
Dynamic equilibrium can only occur in a closed system as none of the reactants or products are able to leave the reaction vessel
In a reversible reaction, when is the concentration of the reactants the highest?
In a reversible reaction, the concentration of the reactants is highest at the start of the reaction.
How does the rate of the reverse reaction change during a reversible reaction?
The rate of the reverse reaction will increase until the system reaches dynamic equilibrium.
Define the term reversible reaction.
A reversible reaction is a reaction that can occur in both directions: the forward reaction (which forms the products) and the reverse direction (which forms the reactants).
How are reversible reactions represented in chemical equations?
Reversible reactions are represented using two opposing arrows, ⇌.
If the forward reaction of a reversible reaction is exothermic, what is the energy change of the reverse reaction?
If the forward reaction of a reversible reaction is exothermic, the reverse reaction is endothermic.
What happens to macroscopic properties in dynamic equilibrium?
In dynamic equilibrium, there is no change in macroscopic properties such as color and density as they depend on concentration.
True or False?
In dynamic equilibrium, the concentrations of reactants and products are equal.
False.
In dynamic equilibrium, the concentrations of reactants and products are constant, not necessarily equal.
True or False?
Equilibrium can be reached in open flasks for reactions taking place entirely in solution.
True.
Equilibrium can be reached in open flasks for reactions taking place entirely in solution.
True or False?
Dynamic equilibrium can only be approached from the reactants side.
False.
Dynamic equilibrium can be approached starting with either reactants or products.
What is the key difference between closed and open systems for gas reactions?
For reactions involving gases, equilibrium can only be reached in a closed system, not in an open system.
Define the equilibrium constant expression.
The equilibrium constant expression is an equation that links the equilibrium constant, K, to the concentrations of reactants and products at equilibrium, taking into account the stoichiometry of the equation.
State the general form of the equilibrium constant expression for the reaction
aA + bB ⇌ cC + dD.
The general form of the equilibrium constant expression is:
K = [C]c [D]d / [A]a [B]b
True or False?
Solids are included in equilibrium constant expressions.
False.
Solids are ignored in equilibrium constant expressions.
What do the square brackets represent in the equilibrium constant expression?
The square brackets represent the equilibrium concentrations of the substances in mol dm-3.
True or False?
The equilibrium constant, K, is specific to a given equation.
True.
The equilibrium constant, K, is specific to a given equation.
What happens to the equilibrium constant expression when a reaction equation is reversed?
When a reaction equation is reversed, the equilibrium constant becomes the reciprocal of the original K value.
True or False?
The equilibrium constant expression uses initial concentrations of reactants and products.
False.
The equilibrium constant expression uses equilibrium concentrations of reactants and products.
What units are typically used for concentrations in equilibrium constant expressions?
Concentrations in equilibrium constant expressions are typically expressed in mol dm-3.
True or False?
The equilibrium constant expression always includes all species in the balanced equation.
False.
The equilibrium constant expression excludes solids and pure liquids.
What does the size of the equilibrium constant, K, indicate?
The size of the equilibrium constant, K, indicates how the equilibrium mixture is made up with respect to reactants and products.
True or False?
When K > 1, the equilibrium lies to the left hand side.
False.
When K > 1, the equilibrium lies to the right hand side (products are favored).
What does it mean when K >> 1?
When K >> 1, the equilibrium lies far over to the right hand side and the reaction almost goes to completion.
True or False?
When K < 1, the concentration of products is greater than the concentration of reactants.
False.
When K < 1, the concentration of reactants is greater than the concentration of products.
What does K = 1 indicate about the equilibrium mixture?
When K = 1, there are significant amounts of both reactants and products, and equilibrium does not lie in favor of either.
Is K constant at all temperatures?
No, K is constant at a specified temperature but can change with temperature.
True or False?
Stronger acids always have a higher value of K than weaker acids.
True.
Stronger acids always have a higher value of K than weaker acids.
Define the relationship between K and K' for reverse reactions.
K' = 1/K or K' = K-1, where K' is the equilibrium constant for the reverse reaction.
True or False?
The equilibrium constant, K, is affected by changes in concentration of reactants or products at a given temperature.
False.
The equilibrium constant, K, is not affected by changes in concentration of reactants or products at a given temperature.
What is Le Chatelier's principle?
Le Chatelier's principle states that if a change is made to a system at dynamic equilibrium, the position of the equilibrium moves to minimise this change.
True or False?
Increasing the concentration of a reactant shifts the equilibrium to the left.
False.
Increasing the concentration of a reactant shifts the equilibrium to the right.
How does decreasing the concentration of a product affect the equilibrium?
Decreasing the concentration of a product shifts the equilibrium to the right to reduce the effect of the decrease.
How does an increase in pressure affect a gas equilibrium?
An increase in pressure shifts the equilibrium in the direction that produces the smaller number of gas molecules.
True or False?
Changes in pressure always affect the position of equilibrium.
False.
Changes in pressure only affect reactions where the reactants or products are gases, and the number of moles of gaseous reactant are different to the number of moles of gaseous product.
How does an increase in temperature affect an endothermic reaction?
An increase in temperature shifts the equilibrium in the endothermic direction, favoring the products for an endothermic reaction.
True or False?
Catalysts have no effect on the position of equilibrium.
True.
Catalysts have no effect on the position of equilibrium or the value of K.
What effect do catalysts have on a reaction at equilibrium?
Catalysts only cause a reaction to reach its equilibrium faster, without affecting the position of equilibrium.
How does Le Chatelier's principle apply to heterogeneous equilibria?
Le Chatelier's principle can be applied to heterogeneous equilibria in the same way as homogeneous equilibria, considering the effects of changes in concentration, pressure, and temperature.
True or False?
If the forward reaction is exothermic, the backward reaction is favoured by increasing the temperature.
True.
If the forward reaction is exothermic, the backward reaction is favoured by increasing the temperature.
In the following system, would an increase or decrease in pressure favour the forward reaction?
2A + 2B ⇌ C + D
Increasing the pressure would favour the forward reaction.
This is because there are 4 molecules on the left and side and 2 molecules on the right hand side.
An increase in pressure will favour the side with the fewest number of molecules.
If the forward reaction is endothermic, would a high or low temperature increase the yield of products?
If the forward reaction is endothermic, a high temperature would increase the yield of products.
This is because the forward reaction is endothermic. A high temperature would favour the endothermic pathway to oppose the increase.
True or False?
A catalysts only speeds up the rate of the forward reaction in a reversible reaction.
False.
A catalyst speeds up the rate of both the forward and backward reactions.
True or False?
Increasing pressure shifts the equilibrium to favour the side with more gas molecules.
False.
Increasing pressure shifts the equilibrium to favour the side with fewer gas molecules.
If the concentration of a reactant decreases, how does the equilibrium shift?
Equilibrium shifts to the left to reduce the effect of a decrease in reactant (or an increase in the concentration of product).
If the pressure decreases, how does the equilibrium of a reaction shift?
Equilibrium shifts in the direction that produces the larger number of molecules of gas to increase the pressure again.