equil, Kc Flashcards

1
Q

def: dynamic

A

the forward and backward reactions proceed at equal rates

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2
Q

def: equilibrium

A

the concentration of the reactants and products are constant

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3
Q

def: le chatelier’s principle

A

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

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4
Q

how is dynamic equilibrium reached?

A

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.

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5
Q

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

A

equilibrium position is on the right

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6
Q

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

A

equilibrium position is on the left

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7
Q

pressure only affects reactions involving…

A

gases
(the more moles = the greater the pressure)

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8
Q

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

A

fewest

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9
Q

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

A

most

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10
Q

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

A

no effect

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11
Q

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

A

increase

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12
Q

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

A

decrease

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13
Q

def: catalyst and how does it work

A

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

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14
Q

when a catalyst is added to a reversible reaction:

A

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

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15
Q

an increase in temperature favours the …. direction

A

endothermic

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16
Q

a decrease in temperature favours the … direction

A

exothermic

17
Q

when can dynamic equilibrium occur?

A

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

18
Q

what does a reversible arrow mean

A

a reversible reaction

19
Q

if the concentration of a reactant is increased:

A

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

20
Q

if the concentration of a product is increased:

A

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

21
Q

if the concentration of a product is decreased:

A

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

22
Q

if the concentration of a reactant is decreased:

A

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

23
Q

exothermic reactions

A

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

24
Q

endothermic reactions

A

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

25
why are catalysts added to reversible reactions?
to reduce the time taken to reach dynamic equilibrium
26
def: compromise conditions
choosing conditions which produce maximum yield of product, in shortest amount of time, for least cost
27
why are compromise conditions neccessary?
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
28
Kc
[products] over [reactants] [ ] = concentration (moldm-3) c means concentration molar ratio = [ ] times to power of ? ICEE
29
If Kc / Kp is exactly 1:
conc of products is equal to conc of reactants, equillibirum is in middle
30
If Kc / Kp is greater than 1:
more products than reactants at equilibrium, equillibirum shifted to the right
31
If Kc / Kp less than 1
more reactants than products at equilibrium, equillibirum shifted to the left
32
def: homogenious reaction
system where all the reactants and products are in the same phase
33
Kp
(pp products) over (pp reactants) p means pressure (kPa) gas phase equilibria reactions ICEMP
34
what is a partial pressure?
the contribution one gas makes, also the sample of gas it could create if in a container on its own
35
equation of partial pressure of A:
mole fraction of A x total pressure
36
equation for mole fraction of A
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)
37
which condition only can affect Kp of Kc value?
temperature
38
what happens to the value of Kp if temperature increases?
value of Kp decreases
39
what happens to the value of Kp if temperature decreases?
value of Kp increases