Reversible reactions and dynamic equilibrium (6.2) (M)

Question 1

What is a reversible reaction?

Answer 1

Reaction in which the products of the reaction can react to produce the original reactants

under certain conditions

Question 2

How can a reversible reaction be represented?

Answer 2

A double-headed arrow (⇌)

Question 3

How can you change the direction of reversible reactions

Answer 3

By changing the conditions.

Question 4

How do the directions of a reversible reaction apply to exothermic and endothermic conditions?

Answer 4

If a reversible reaction is exothermic in one direction, it is endothermic in the opposite direction

Question 5

If a reversible reaction is exothermic and endothermic, how does energy in each reaction compare?

Answer 5

The same amount of energy is transferred in both the forwards and reverse reaction

Question 6

In the exothermic and endothermic directions, the (…) amount of energy is transferred each way

Answer 6

same

Question 7

Why might there be a loss in mass after a reaction in a reversible reaction?

Answer 7

Not all of reactant will react in a reversible reaction because the reaction does not go to completion

Question 8

What is a closed system?

Answer 8

Chemical reaction that happens in apparatus which prevents the escape of reactants and products

Question 9

When is equilibrium reached?

Answer 9

When the forward and reverse reactions occur at exactly the same rate

Question 10

The relative amounts of all the reactants and products at equilibrium depend on what?

Answer 10

The conditions of the reaction

Question 11

The effects of changing conditions on a system at equilibrium can be predicted using what?

Answer 11

Le Chatelier’s principle

Question 12

What is Le Chatelier’s principle?

Answer 12

If a system is at equilibrium and a change is made to any of the conditions, then the system responds to counteract the change

Question 13

What happens if the concentration of one of the reactants or products is changed in equilibrium?

Answer 13

the system is no longer at equilibrium and the concentrations of all the substances will change until equilibrium is reached again

Question 14

What happens in equilibrium If the concentration of a reactant is increased?

Answer 14

more products will be formed until equilibrium is reached again

(less reactants formed than products)

Question 15

What will happen in equilibrium if the concentration of a product is decreased?

Answer 15

more reactants will react until equilibrium is reached again

Question 16

2 things

What if the temperature of a system at equilibrium is increased?

Answer 16

• the relative amount of products at equilibrium increases for an endothermic reaction (increase at endo)
• the relative amount of products at equilibrium decreases for an exothermic reaction (decrease at exo)

Question 17

2 things

What happens if the temperature of a system at equilibrium is decreased?

Answer 17

• the relative amount of products at equilibrium decreases for an endothermic reaction
• the relative amount of products at equilibrium increases for an exothermic reaction

Question 18

For gaseous reaction at equilibrium, what does an increase in pressure cause?

Answer 18

the equilibrium position to shift towards the side with the smaller number of molecules as shown by the symbol equation for that reaction

(if side with smaller number of molecules are the products, the reactants to products symbol will be bigger)

Question 19

For gaseous reactions at equilibrium, what does a decrease in pressure cause?

Answer 19

causes the equilibrium position to shift towards the side with the larger number of molecules as shown by the symbol equation for that reaction

(if side with smaller number of molecules are the products, the products to reactants symbol will be bigger)

Question 20

What is the effect of a catalyst on equilibrium yield? Why?

Answer 20

no effect/change

because a catalyst increases the rate of the forward
and reverse reactions equally

Question 21

Why might a change in pressure not affect the equilibrium mixture?

Answer 21

there may be no gases present

so no change in equilibrium position