equil, Kc

Question 1

def: dynamic

Answer 1

the forward and backward reactions proceed at equal rates

Question 2

def: equilibrium

Answer 2

the concentration of the reactants and products are constant

Question 3

def: le chatelier’s principle

Answer 3

the position of equilibrium will shift to oppose change made to the system

Question 4

how is dynamic equilibrium reached?

Answer 4

at the start of the reaction, forward reaction is fast and backward reaction is slow;
after start, backward reaction speeds up as the forward reaction slows;
the rate of the forward reaction becomes the same as the rate of the backward reaction.

Question 5

what is the equilibrium position when there are more products than reactants?

Answer 5

equilibrium position is on the right

Question 6

what is the equilibrium position when there are more reactants than products?

Answer 6

equilibrium position is on the left

Question 7

pressure only affects reactions involving…

Answer 7

gases
(the more moles = the greater the pressure)

Question 8

an increase in pressure will always move the equilibrium to the side with the ….. moles

Answer 8

fewest

Question 9

a decrease in pressure will always move the equilibrium to the side with the … moles

Answer 9

most

Question 10

if there is an equal number of moles, a change in pressure leads to ….

Answer 10

no effect

Question 11

a decrease in volume of container , leads to an …. in pressure

Answer 11

increase

Question 12

an increase in volume of container, leads to a …. in pressure

Answer 12

decrease

Question 13

def: catalyst and how does it work

Answer 13

a substance that speeds up the rate of reaction without being used up;
provided an alternative reaction pathway with a lower activation energy

Question 14

when a catalyst is added to a reversible reaction:

Answer 14

rate of both forward and backwards reaction increase equally by the same amount;
there is no change to the position of the equilibrium;
dynamic equilibrium is reached faster

Question 15

an increase in temperature favours the …. direction

Answer 15

endothermic

Question 16

a decrease in temperature favours the … direction

Answer 16

exothermic

Question 17

when can dynamic equilibrium occur?

Answer 17

only occurs if the reversible reaction is carried out in a sealed container so no product can escape - closed system

Question 18

what does a reversible arrow mean

Answer 18

a reversible reaction

Question 19

if the concentration of a reactant is increased:

Answer 19

the equilibrium will shift to the right, to oppose the addition of [reactant],
so yield of [product] increases

Question 20

if the concentration of a product is increased:

Answer 20

the equilibrium will shift to the left, to oppose the addition of [product]
so yield of [reactants] increase

Question 21

if the concentration of a product is decreased:

Answer 21

the equilibrium will shift to the right,
to oppose the decrease in [products],
so yield of [product] increases

Question 22

if the concentration of a reactant is decreased:

Answer 22

the equilibrium will shift to the left,
to oppose the decrease in [reactants],
so yield of [reactant] increases

Question 23

exothermic reactions

Answer 23

releases heat energy,
temperature of surroundings increase,
enthalpy change is negative (minus delta H)

Question 24

endothermic reactions

Answer 24

absorb heat energy,
temperature of surroundings decrease,
enthalpy change is positive (plus delta H)

Question 25

why are catalysts added to reversible reactions?

Answer 25

to reduce the time taken to reach dynamic equilibrium

Question 26

def: compromise conditions

Answer 26

choosing conditions which produce maximum yield of product,
in shortest amount of time,
for least cost

Question 27

why are compromise conditions neccessary?

Answer 27

higher pressure would be too expensive
450 degrees C gives a good yield in a fast time
catalyst doesn’t affect position of equilibrium, but reduces cost of reaction as less fossil fuel burned to generate heat energy

Question 28

Kc

Answer 28

[products] over [reactants]
[ ] = concentration (moldm-3)
c means concentration
molar ratio = [ ] times to power of ?
ICEE

Question 29

If Kc / Kp is exactly 1:

Answer 29

conc of products is equal to conc of reactants,
equillibirum is in middle

Question 30

If Kc / Kp is greater than 1:

Answer 30

more products than reactants at equilibrium,
equillibirum shifted to the right

Question 31

If Kc / Kp less than 1

Answer 31

more reactants than products at equilibrium,
equillibirum shifted to the left

Question 32

def: homogenious reaction

Answer 32

system where all the reactants and products are in the same phase

Question 33

Kp

Answer 33

(pp products) over (pp reactants)
p means pressure (kPa)
gas phase equilibria reactions
ICEMP

Question 34

what is a partial pressure?

Answer 34

the contribution one gas makes,
also the sample of gas it could create if in a container on its own

Question 35

equation of partial pressure of A:

Answer 35

mole fraction of A x total pressure

Question 36

equation for mole fraction of A

Answer 36

no. of moles of A in equil mixture / total no. of moles of all gases at equil

(all molar fractions within a mixture should always add up to 1)

Question 37

which condition only can affect Kp of Kc value?

Answer 37

temperature

Question 38

what happens to the value of Kp if temperature increases?

Answer 38

value of Kp decreases

Question 39

what happens to the value of Kp if temperature decreases?

Answer 39

value of Kp increases