Reversible Reactions And Equilibrium
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What are reversible reactions
Reactions which can go both ways
What is a reversible reaction indicated by
A double arrow
What is the equation for the reversible reaction of dehydrating copper sulfate
CuSO4 . 5H2O (s) double arrow CuSO4(s) + 5H2O(l) Hydrate copper sulfate double arrow water + anhydrous copper sulfate
What is the equation for the reversible reaction of heating ammonium chloride
NH4Cl double arrow NH3 + HCl Ammonium chloride double arrow ammonia + hydrogen chloride (gas)
What is observed when the copper sulfate is heated
It turns white
What type of reaction is heating copper sulfate
Endothermic
What is observed when water is added to the anhydrous copper sulfate
-turns blue -heat released
What type of reaction is adding water to anhydrous copper sulfate
Exothermic
Why is a mineral wool plug used when heating ammonium chloride
To prevent the gases from escaping the boiling tube once heated
How is equilibrium achieved
-When reversible reactions happen in a closed system so no reactants or products can enter or leave -as the reactants collide and turn into products, the concentration of reactants decreases -hence the rate of the forward reaction decrease -simultaneously the rate of the reverse reaction increases until eventually forward and reverse reactions happen at the same rate
What is a dynamic equilibrium
-where the reactions are continuing but the forwards and reverse reactions occur at the same rate -the concentration of reactants and products remain constant
Draw reversible reaction graphs for rate of reaction and concentration
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What is Le Chateliers principal
If a dynamic equilibrium is disturbed by changing the conditions we find that the position of the equlibrium shifts as if to counteract the change
What is the effect of changing the pressure on the position of equilibrium
-increase in pressure shifts the position of the equilibrium in the direction that produces fewer moles of gas -decrease in pressure shifts the position of the equilibrium in the direction that produces more moles of gas ⛽️
If there are two moles on the left hand side of the arrow and one mole on the right hand side of the arrow what happens when we increase the pressure
The equilibrium shifts to the right hand side (side with fewer moles)
What does the changing of pressure on an equilibrium only affect
Gases
What is the effect of changing the temperature on the position of equilibrium in a reversible reaction
-increase in temperature shifts the position of equilibrium in the direction of the endothermic reaction. Yield from the exothermic reaction decrease and yield from endothermic reaction increases. -decrease in temperature shifts the position of equilibrium in the direction of the exothermic reaction. Yield from exothermic reaction increases and yield from endothermic reaction decreases.
How does increasing and decreasing the temperature affect the position of equilibrium is the energy change is negative
INCREASE -forward reaction is exothermic -favours endothermic reaction -equilibrium shifts to the left DECREASE -forward reaction is exothermic -favours exothermic reaction -equilibrium shifts to the right
How does increasing and decreasing the temperature affect the position of equilibrium when the energy change is positive
INCREASING -forward reaction is endothermic -favours endothermic -equilibrium shifts to the right DECREASING -forward reaction is endothermic -favours exothermic -equilibrium shifts to the left
What happens to equilibrium when temperatures increases
-Equilibrium shifts to the endothermic side -yield of endothermic side increases -yield of exothermic side decreases
What happens to the equilibrium when the temperature decreases
-equilibrium shifts to the exothermic side -exothermic yield increases -endothermic yield decreases
What is the effect of a catalyst on the position of equilibrium
-no effect on the position of the equilibrium -the rate of both forward and reverse reaction increases by the same amount -activation energy of both the forward and reverse reactions decreases by the same amount
What is the equation of the reversible reaction between ice and water
H2O (s) double arrow H2O (l)
Why can the reversible reaction between ice and water not reach a state of equilibrium
The system is not closed