Dynamic Equilibrium

Question 1

what is a reversible reaction

Answer 1

reaction can occur in both directions: the forward reaction (which forms the products) and the reverse direction (which forms the reactants)

Question 2

what does it mean when it is in ‘dynamic equilibrium’

Answer 2

the molecules on the left and right of the equation are changing into each other by chemical reactions constantly and at the same rate and The concentration of reactants and products remains constant

Question 3

what does a reversible reaction occur in

Answer 3

a closed system so that none of the participating chemical species are able to leave the reaction vessel

Question 4

explain the dynamic equilibrium reaction during the Haber process

Answer 4

nitrogen and hydrogen are present at the beginning of the reaction, the rate of the forward reaction is at its highest, since the concentrations of hydrogen and nitrogen are at their highest
the concentrations of hydrogen and nitrogen gradually decrease, so the rate of the forward reaction will decrease
The concentration of ammonia is gradually increasing and so the rate of the backward reaction will increase
the rate of the forward reaction and the rate of the backward reaction will eventually become equal and equilibrium is reached:

Question 5

what are the three things that can change the position of equilibrium

Answer 5

temperature / pressure / concentration

Question 6

what is Le Chatelier’s principle

Answer 6

if there is a change to one of the conditions the equilibrium will move to oppose the change

Question 7

What happens if you increase the temperature in a reversible reaction

Answer 7

Equilibrium moves in the endothermic

direction to reverse the change

Question 8

what happens if you decrease temperature

Answer 8

Equilibrium moves in the exothermic

direction to reverse the change

Question 9

what happens if you increase pressure

Answer 9

Equilibrium shifts in the direction that
produces the smaller number of molecules
of gas to decredse the pressure again

Question 10

what happens if you decrease pressure

Answer 10

Equilibrium shifts in the direction that
produces the larger number of molecules
of gas to decrease the pressure again

Question 11

what happens if you increase concentration

Answer 11

Equilibrium shifts to the right to reduce the
effect of increasing the concentration of
dredctant

Question 12

what happens if you decrease concentration

Answer 12

Equilibrium shifts to the left to reduce the
effect of a decrease in reactant (or an
increase in the concentration of product)

Question 13

What 3 things should be thought about when designing industrial process

Answer 13

• the cost of extraction of raw materials is too high or they are unavailable then the process is no longer economically viable / is it profitable
• require huge amounts of heat and pressure which is very expensive to maintain
• controlling conditions for maximum yield

Question 14

What factors increase the rate of reaching equilibrium

Answer 14

• increasing temp - higher kinetic energy
• increasing pressure - more collisions
• higher concentration is used as there are more particles per given volume, hence there are more collisions
• A catalyst is used as it speeds up the rate of reaction, allowing it to reach equilibrium faster

Question 15

what happens if you don’t use a catalyst

Answer 15

you would have to increase temperature which reduce the yield of the ammonia ever further

Question 16

using the example of the: Haber Process

which way would high pressure favour and why

Answer 16

the forward reaction as there are fewer moles of gas of products so more product will be produced so pressure set as high as possible for maximum yield of products
200 atm is the compromise for safety and economically

Question 17

using the example of the: Haber Process

what would increasing temp do to the reversible reaction and why

Answer 17

A higher temperature would favour the reverse reaction as it is endothermic (takes in heat) so a higher yield of reactants would be made which is the opposite of what we want therefore greater at lower temperature for higher yield of products

however this is don’t at a compromise because it will be too slow so 450 degrees allows compromise between high rate of reaction and yield of products formed

Question 18

why is a catalyst important

Answer 18

because catalyst increases the rate of both the forward and backward reactions by the same amount (by providing an alternative pathway requiring lower activation energy)
concentration of reactants and products is nevertheless the same at equilibrium as it would be without the catalyst.
So a catalyst is used as it helps the reaction reach equilibrium quicker

Question 19

what happens if this reaction was done with out a catalyst

Answer 19

we would have to increase temperature hence increasing costs and decreasing yield as the higher temperature decomposes more of the NH3 molecules into reactants