What makes a reaction reversible, why the energy change is equal and opposite in each direction, and what dynamic equilibrium actually means.
You can study this deck without signing up — your progress is kept in this browser. An account saves it properly, syncs it across devices, and lets you edit the cards.
1.What is a reversible reaction?
One in which the products can react to re-form the original reactants.
2.What symbol is used for a reversible reaction?
Two half arrows pointing in opposite directions, rather than a single arrow.
3.Give an example of a reversible reaction.
Heating hydrated copper sulfate drives water off to give the anhydrous form, and adding water reverses it.
4.What colour change is seen with copper sulfate?
Blue hydrated copper sulfate turns white when heated, and back to blue when water is added.
5.If a reversible reaction is exothermic one way, what is it the other way?
Endothermic, by exactly the same amount of energy.
6.Why must the energy changes be equal and opposite?
The same bonds are being broken and formed, just in the opposite order, so the energy involved is the same.
7.What is equilibrium?
The point in a closed system where the forward and reverse reactions are happening at exactly the same rate.
8.Why is it called dynamic equilibrium?
Both reactions are still going on all the time. It is only the amounts that stay constant, not the activity.
9.What is a closed system?
One where no reactants or products can enter or leave.
10.Why can equilibrium only be reached in a closed system?
If products could escape, the reverse reaction could never keep pace, so the rates could never become equal.
11.Do the amounts of reactants and products stay equal at equilibrium?
No. They stay constant, but they are usually not equal to each other.
12.What does it mean if equilibrium lies to the right?
There are more products than reactants in the mixture at equilibrium.
13.What does it mean if equilibrium lies to the left?
There are more reactants than products in the mixture at equilibrium.
14.What happens to the rate of the forward reaction as equilibrium is approached?
It decreases, because the reactants are being used up.
15.What happens to the rate of the reverse reaction as equilibrium is approached?
It increases, because more product is available to react back.
16.What is true about the two rates at equilibrium?
They are equal, so there is no overall change in the amounts of anything.
17.Does a reaction stop at equilibrium?
No. Both reactions continue at the same rate, which is why nothing appears to change.
18.What is thermal decomposition of ammonium chloride an example of?
A reversible reaction: it decomposes on heating and re-forms on cooling.
19.Why does a reversible reaction never give a 100 per cent yield?
Some product is always converting back into reactants, so not all the reactant can be converted.
20.What conditions affect the position of an equilibrium?
Concentration, temperature and, for gases, pressure.
21.Does a catalyst change the position of equilibrium?
No. It speeds up the forward and reverse reactions equally, so equilibrium is reached sooner but at the same position.
22.Why is a catalyst still useful for a reversible reaction?
It reaches the same equilibrium position in less time, which matters commercially.
23.What would you observe at equilibrium in a coloured system?
The colour stops changing, even though both reactions are still occurring.
24.How is anhydrous copper sulfate used as a test?
It turns from white to blue in the presence of water, so it tests for water.
You remember far more by trying to recall an answer than by reading it. Run these as flashcards and the ones you keep getting wrong will come back more often.
Start studyingOr see the other The Rate and Extent of Chemical Change decks.