Topic 6- Equilibria Flashcards Preview

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Flashcards in Topic 6- Equilibria Deck (7)
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1

Why is the forward reaction fastest at the start?

When does the forward reaction slow down?

What then happens to the backward reaction?

What happens at equilibrium?

What is a reversible chemical reaction known as?

How can the position at equilibrium be varied by?

What does dynamic mean?

What are and state the two conditions at equilibrium?

As there's no backward reaction

As reactants are used up

The backward reaction starts to increase

The backward and forward reaction rates are equal and opposite

A dynamic process

Changing certain conditions

That both reactions are proceeding at the same time

-The rate of the forward reaction equals the rate of the backward reaction
-Concentrations of all reactants and products remain constant.

2

When can dynamic equilibrium only happen?

What happens if you change the concentration, pressure or temperature of a reversible reaction?

What happens if the position of equilibrium moves to the left?

What happens if the position of equilibrium moves to the right?

In a closed system- ie nothing can get in or out

You're going to alter the position of equilibrium

You'll get more reactants

You'll get more products.

3

What is the definition of Le Chatelier's Principle?

What does this basically mean?

When a change is applied to a closed system in dynamic equilibrium, the system moves in such a way as to oppose the effect of the change

If a reaction at equilibrium is subjected to a change in concentration, pressure or temperature, the position of equilibrium will move to counteract the change.

4

What does changing pressure only affect?

When does no change occur to the equilibrium if there's a change in pressure?

What does an increase in pressure do to the equilibrium?

What does a decrease in pressure do to the equilibrium?

What does the direction of movement in equilibrium if there's a change in temperature depend on?

Describe the what happens to the equilibrium if there's an increase and decrease in temperature in an:

Exothermic reaction

Endothermic reaction

Equilibria involving gases

No change occurs when equal number of gaseous molecules appear on both sides

Moves to the side with fewer gaseous molecules

Moves to the side with more gaseous molecules

The sign of the enthalpy change

Exothermic-
Increase in temperature= to the left ; decrease in temperature= to the right

Endothermic-
Increase in temperature= to the right ; decrease in temperature= to the left.

5

What does adding a catalyst not affect in a reaction?

What does adding a catalyst not increase but what do they do?

Adding a catalyst doesn't affect the position of equilibrium

Adding a catalyst can't increase yield- but they do mean equilibrium is reached faster.

6

What does increasing the temperature mean?

What does the equilibrium shift to and why?

What does decreasing the temperature mean?

What does the equilibrium shift to?

Why is this?

What does it mean if the forward reaction's endothermic?

Adding heat

The equilibrium shifts in the endothermic (positive delta H) direction to absorb this heat

Removing heat

The equilibrium shifts in the exothermic (negative delta H) direction

To produce more heat, in order to counteract the drop in temperature

The reverse reaction will be exothermic, and vice versa.

7

What does using Le Chatelier's principle to work out what effect changing certain conditions has on the position of equilibrium only apply to?

Describe this?

This only applies to homogeneous Equilibria

Reactions where every species is in the same physical state (eg all liquid or all gas).