Paper Together: sit a paper in a room with your friends.See how it works
A second set of questions on reversible reactions and equilibrium. They are different from the ones on the topic page. Try each, then open the answer and compare your working.
The forward reaction is endothermic. What happens to the yield of products if the temperature is increased?
Answer: it increases
Does a catalyst change the yield at equilibrium? Answer yes or no.
Answer: no
In 2SO₂ + O₂ ⇌ 2SO₃, how many gas molecules are on the left side?
Answer: 3
A reaction at equilibrium is exothermic in the forward direction. What happens to the yield of products if the temperature is increased?
Answer: it decreases
For H₂ + I₂ ⇌ 2HI there are the same number of gas molecules on each side. Explain what happens to the position of equilibrium when the pressure is increased.
Answer: it does not change because there are the same number of gas molecules on each side
N₂O₄ ⇌ 2NO₂ is endothermic in the forward direction. What happens to the amount of NO₂ if the temperature is lowered?
Answer: it decreases
Explain why the Haber process uses a compromise temperature of about 450 °C.
Answer: a lower temperature gives a higher yield but the rate would be too slow
In a closed container, the equilibrium CO + 2H₂ ⇌ CH₃OH is established. More H₂ is added. State and explain the effect on the position of equilibrium.
Answer: it shifts to the right to use up the extra hydrogen
On a graph of concentration against time for a reversible reaction in a closed container, both lines become flat after 6 minutes. What does this show?
Answer: equilibrium has been reached
A student says that at equilibrium the reactions have stopped because the concentrations do not change. Explain why the student is wrong.
Answer: both reactions are still happening at the same rate
Short questions with options. Choose one before you open the answer.
What does ⇌ mean?
A reversible reaction.
What is a closed system?
One in which nothing can enter or leave.
What is dynamic equilibrium?
The forward and reverse reactions happen at the same rate in a closed system.
Are the concentrations equal at equilibrium?
Not necessarily. They are constant.
What does Le Chatelier’s principle say?
A system at equilibrium moves to oppose a change.
What happens if reactant concentration is increased?
The equilibrium shifts to the right.
What happens if pressure increases?
The equilibrium shifts to the side with fewer gas molecules.
What happens if temperature increases?
The equilibrium shifts in the endothermic direction.
What happens if temperature decreases?
The equilibrium shifts in the exothermic direction.
What is the effect of a catalyst on the position of equilibrium?
None.
What is the effect of a catalyst on the time to reach equilibrium?
It is shorter.
What colour change shows hydrated copper sulfate being heated?
Blue to white.
What is the position of equilibrium?
The relative amounts of reactants and products at equilibrium.
If the forward reaction is exothermic, what is the reverse?
Endothermic.
Why is a compromise temperature used in the Haber process?
A low temperature gives a higher yield but the rate is too slow.
What is a reversible reaction?
One where the products can react to make the reactants again.
What colour is anhydrous copper sulfate?
White.
What happens when water is added to white copper sulfate?
It turns blue and gives out heat.
What happens to the amounts of reactants and products at equilibrium?
They stay constant.
Why is it called a dynamic equilibrium?
Both the forward and reverse reactions are still happening.
What does it mean if the position of equilibrium is to the right?
There are more products than reactants.
What happens if a product is removed from an equilibrium mixture?
The position shifts right to make more product.
What happens to the position of equilibrium if the pressure decreases?
It shifts to the side with more gas molecules.
Does pressure change the position if both sides have equal gas molecules?
No.
How many gas molecules are on the left of N₂ + 3H₂ ⇌ 2NH₃?
Four.
Why does a graph of concentration against time go flat at equilibrium?
The forward and reverse reactions are still happening at the same rate, so the amounts stop changing.
Yumio is not affiliated with, endorsed by or connected to AQA, Pearson Edexcel or any other exam board.