1.6 - Equilibria and Redox Reactions

Question 1

What is dynamic equilibrium?

Answer 1

As the reactant gets used up, the forward reaction slows down - and as more product is formed, the reverse reaction speeds up. After a while, the forward reaction will be going at exactly the same rate as the backward reaction; the concentrations of the reactants and products will not be changing anymore so it appears that nothing is happening

Question 2

What is a closed system?

Answer 2

Nothing can get in or out of the reaction

Question 3

What two things are needed for dynamic equilibrium to happen?

Answer 3

A closed system and a constant temperature

Question 4

What does changing the position of equilibrium mean?

Answer 4

This means that you’ll end up with different amounts of reactants and products at equilibrium

Question 5

What is le Chatelier’s Principle?

Answer 5

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

Question 6

Do catalysts change the position of equilibrium?

Answer 6

Catalysts have no effect on the position of equilibrium but they do make sure the equilibrium is reached faster

Question 7

How does increasing the concentration of the reactant affect the position of equilibrium?

Answer 7

If you increase the concentration of a reactant, the equilibrium tries to get rid of the extra reactant by making more product - the equilibrium is shifted to the right

Question 8

How does increasing the concentration of the product affect the position of equilibrium?

Answer 8

If you increase the concentration of the product, the equilibrium tries to remove this extra product, making the reverse reaction happen faster so the equilibrium shifts to the left

Question 9

What state of matter does changing the pressure affect the position of equilibrium?

Answer 9

In gases

Question 10

What happens to the position of equilibrium when you increase the pressure?

Answer 10

Increasing the pressure shifts the equilibrium to the side with fewer gas molecules

Question 11

What happens to the position of equilibrium when you decrease the pressure?

Answer 11

Decreasing the pressure shifts the equilibrium to the side with more gas molecules

Question 12

What happens to the position of equilibrium when the temperature increases?

Answer 12

The equilibrium shifts in the endothermic direction

Question 13

What happens to the position of equilibrium when the temperature decreases?

Answer 13

The equilibrium shifts to the exothermic direction

Question 14

What are compromised conditions?

Answer 14

Compromised conditions aim to make the most amount of product in the shortest amount of time

Question 15

What is the equilibrium constant?

Answer 15

The equilibrium constant is the ratio worked out from the concentrations of the products and reactants after equilibrium is reached

Question 16

What is the equation for Kc?

Answer 16

For a general reaction of aA + bB ⇌ dD + eE:

[D]^d [E]^e) / [A]^a [B]^b

Question 17

What do the square brackets mean in regards to equilibrium?

Answer 17

Square brackets mean concentration in mol/dm3

Question 18

How are equilibrium concentrations calculated?

Answer 18

1) Find out how many moles of each reactant and product there at equilibrium
2) Calculate the molar concentrations of each reactant and product by dividing each number of moles by the volume of the reaction. The volumes must be in dm3

Question 19

How does Kc change if more product is formed?

Answer 19

Kc will rise if more products are formed

Question 20

How does Kc change if less product is formed?

Answer 20

Kc will decrease if fewer products are formed

Question 21

How does Kc change if the concentration changes?

Answer 21

Kc will stay the same

Question 22

What is a loss of electrons called?

Answer 22

It is called oxidation

Question 23

What is a gain of electrons called?

Answer 23

It is called reduction

Question 24

What is a redox reaction?

Answer 24

A reaction where oxidation and reduction happen simultaneously

Question 25

What does an oxidising agent do?

Answer 25

It accepts electrons and gets reduced

Question 26

What does a reducing agent do?

Answer 26

It donates electrons and gets oxidised

Question 27

What does the oxidation state of an element tell you?

Answer 27

It tells you the total number of electrons it has donated or accepted

Question 28

What is the oxidation state of an uncombined element or a diatomic element?

Answer 28

0

Question 29

What is the oxidation state of a simple monatomic ion?

Answer 29

It is the same as its charge

Question 30

What are the oxidation states in compounds or compound ions?

Answer 30

Each constituent atom has an oxidation state of its own, and the sum of the oxidation states equals the overall oxidation state. This overall oxidation state is equal to the overall charge of the ion

Question 31

What does the sum of the oxidation states in a neutral compound equal to?

Answer 31

It equals to 0

Question 32

What is the anomaly with the combined oxygen in peroxides?

Answer 32

It’s oxidation state is -1 instead of -2

Question 33

What is the anomaly with combined hydrogen in metal hydrides?

Answer 33

It’s oxidation state is -1 instead of -1

Question 34

How can half-equations for oxidising and reducing agents be combined?

Answer 34

The electrons have to be the same on both sides for them to cancel out

Question 35

How do you write half equations when the oxidising and reducing agents contain oxygen or hydrogen?

Answer 35

You add water or H+ ions on the side that its needed