Chemistry 5.5 Flashcards
Define dynamic equilibrium
Rate of forward reaction equals the rate of the backward reaction. Concentrations of reactants and products remain constant.
Occurs in a sealed container
Why does adding a catalyst not change the position of equilibrium?
A catalyst increases the rate of forward and backward reactions equally.
What symbol is used to represent a reversible reaction?
⇌
What is true about energy of forwards and backwards reaction for any reversible reaction?
Reverse reaction has the opposite energy change but same value
Describe how a metal forms at a cathode
Metal ions gain electrons from negative electrode, metal is reduced. Aluminium ions are attracted to the cathode.
The temperature of a reaction is increased. The forwards reaction for this reaction is exothermic. Describe the effect
Endothermic reaction is favoured
Which is the reverse reaction
Equilibrium moves to the left
The temperature of a reaction is decreased. The forwards reaction for this reaction is exothermic. Explain the effect
Exothermic reaction is favoured, which is the forwards reaction
Equilibrium moves to the right
N2 + 3H2 –> 2NH3
The pressure of this reaction is increased. Explain the effect of this change of the yield of ammonia.
Reaction which produces fewer moles of gas is favoured, which is forwards reaction.
Equilibrium moves to the right.
Yield of ammonia increases
N2 + 3H2 –> 2NH3
The pressure of this reaction is decreased. Explain the effect of this change of the yield of ammonia.
Reaction which produces more moles of gas is favoured, which is the backwards reaction. Equilibrium moves to the left. Yield of ammonia decreases
How do you know which reaction produces more moles of gas?
Look at the big numbers in front of each compound/element. If it has no number, use number 1. Add these up on each side. Whichever has the largest number has more moles of gas.
Describe how the dehydration/hydration of copper sulfate crystals are an example of a reversible reaction
Forwards reaction: heat hydrated copper sulfate crystals. Colour change from blue to white.
Backwards reaction: add water to anhydrous copper sulfate. Colour change from white to blue.
Describe how the decomposition of ammonium chloride is a reversible reaction
Forwards reaction: Heat NH4Cl. No change observed as NH3 and HCl are both colourless gases
Backwards reaction: Allow NH3 and Cl to mix in absence of heat. White NH4Cl solid is formed.
Describe how the reversible reaction of the decomposition of ammonium chloride can be observed through a test tube
Gently heat NH4Cl in a test tube. NH4Cl at bottom of tube decomposes to form NH3 and HCl (invisible as both colourless gases).
As the gases rise up the tube, they cool, recombining to form NH4Cl
What is the equation for the decomposition of ammonium chloride?
NH4Cl(s) ⇌ NH3(g) + HCl(g)
What is the equation for the dehydration of copper sulfate?
CuSO4.5H20 ⇌ CuSO4 + H2O
