Reversible Reactions + Dynamic Equilibria

Question 1

What can reversible reactions do that normal reactions can’t?

Answer 1

Well, all reactions can turn reactants into products, but reversible reactions can also turn the products back into reactants

Question 2

Give an example of a non reversible reaction

Answer 2

Magnesium + oxygen -> magnesium oxide

Question 3

In a symbol equation, what’s different for a reversible reaction compared to a normal one

Answer 3

If it’s reversible, we’ll use a specific kind of arrow (the two way one: ⇌), and if it’s not, we’ll use a normal arrow

Question 4

Give an example of a reversible reaction?

Answer 4

Nitrogen + hydrogen ⇌ ammonia

Question 5

What happens after some time after a reversible reaction starts?

Answer 5

Both the forwards and the backwards reaction will happen at the same rate. When this happens, the reaction is in equilibrium

Question 6

What happens to the reactants as a reversible reaction happens (no dynamic equilibrium). Why does this happen?

Answer 6

As reactants go through reactions, their concentration falls so the forward reaction will slow down. This happens cause reactants are being turned into products so conc. decreases. It’s slow because high conc. means high rate and low conc. means low rate.

Question 7

What’s the forwards reaction of a reversible?

Answer 7

The forwards reaction is the ordinary one that all reactions can do- reactants to products

Question 8

What happens to the products as a reversible reaction goes on (no dynamic equilibrium)

Answer 8

More products are being made as the conc. of reactants decrease. And because of this products conc. rises and backward reaction speeds up. This happens because the backwards reaction occurs at the same time as the forward.

Question 9

What happens to the products and reactants when the reaction is in equilibrium? Why does it look like the reaction stopped.

Answer 9

Both reactions are still happening, they’re still going on, but there is no overall affect happening. No products seem to be being made and no reactants seem to be being used up. In reality, it looks like it stopped because the conc. of products and reactants have reached a balance– they’re constant. So when reactants are used up with the forward reaction, the backward reaction turns them back at the same rate. So it looks like nothing happened.

Question 10

What is the condition with the system that must be true for dynamic equilibrium to be achieved. Explain the condition.

Answer 10

Dynamic equilibrium is only reached if the reaction happens in a closed system. A closed system is where no matter can enter or exit the reaction. However, since energy is not matter, it can still be transferred in and out.

Question 11

Dynamic equilibria have three definitive properties. What are they?

Answer 11

They must happen in a closed system (no matter in or out, yes energy in and out)
The forwards and backwards reactions must be happening at the same rate
The conc. of products and reactants have to remain constant (reach a balance)

Question 12

What does position of equilibrium mean? What’s a common misconception.

Answer 12

When a reversible reaction is in equilibrium, it doesn’t necessarily mean that amount of reactants and products are EQUAL, it just means that they’re constant, they remain the same. So position of equilibrium is where the equilibrium leans (it can be different depending on if there are more products than reactants or vice versa)

Question 13

What does it mean if the equilibrium lies to the right?

Answer 13

The amount/concentration of products is greater than that of the reactants

Question 14

What does it mean if the equilibrium lies to the left?

Answer 14

The amount/concentration of the reactants are greater than that of the products

Question 15

Which way equilibrium lies, depend on conditions. What are they?

Answer 15

Temperature
Pressure (gas)
Concentration (of products and reactants)

Question 16

Why can’t catalysts change the position of equilibrium?

Answer 16

They speed up reactions. They do this by lowering activation energy and offering particles a diff. reaction pathway. However, it will do this for both the forward and backwards reactions meaning that although both reactions speed up (equilibrium may even be reached faster), the position of equilibrium doesn’t change)

Question 17

There is another property reversible reactions have that normal ones don’t. Hat is it? (hint: nothing to do with dynamic equilibrium)

Answer 17

Reversible reactions can be both endothermic and exothermic

Question 18

What’s the rule for reversible reactions and exo and endo?

Answer 18

If one reaction (forward/backwards) is exothermic for example, the other one (forward/backwards) will be the opposite. In this example, endothermic

Question 19

Define exothermic. How will an exam show you that a reaction is exo?

Answer 19

Exothermic means a reaction gives energy from reacting particles to surroundings nearby. An exam will tell you normally always about the forward reaction and whether that’s exo or endo. If it’s exo, then delta H (heat inside of particles) will have a negative number next to it, because it’s being taken away from the reaction and there’s an energy decrease. Likewise, delta T (heat energy in surroundings) would have a positive number next to it because energy is being given to it so it’s an increase in energy for it.

Question 20

How do exothermic reactions feel. Give an example of one (general)

Answer 20

Hot. They feel hot. All thermal decomposition reactions are exothermic

Question 21

Give a definition for endothermic. How will an exam convey this information to you

Answer 21

Endothermic takes heat from surrounding and gives it to reacting particles. Exams will normally always tell you about whether the forward reaction is exo or endo. If it’s endo, as a result delta H (heat in particles) experiences an energy increase so the number next to it will be positive. Likewise, delta T (heat in surroundings) experiences an energy decrease, so the number next to it will be negative.

Question 22

How do endothermic reactions feel. List an example of one.

Answer 22

Cold. Endothermic feels cold. Melting is endothermic though you may not think it cause it feels hot. Well energy from surroundings is being used and given to particles inside in order for it to melt. So…