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Equilibrium chapter 19 flashcards (how far?)
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- 1What is a homogeneous equilibrium?This is an equilibrium that contains equilibrium species that all have the SAME state/phase
- 2What is a heterogeneous equilibrium?This is an equilibrium that contains equilibrium species that have DIFFERENT states/phases
- 3What states are included in the Kc expression?In HOMOGENEOUS equilibria, the Kc expression contains concentrations of ALL the species
However, in HETEROGENEOUS equilibria, the concentrations of SOLIDS and LIQUIDS are essentially CONSTANT so any solid/liquid species are OMITTED from the Kc expression - they are AUTOMATICALLY incorporated within the overall equilibrium constant
Kc, therefore, only includes GASEOUS or AQUEOUS species!! - 4What states are included when calculating the units for Kc?Like with the equilibrium expression, when calculating the units for Kc, you also only include the AQUEOUS or GASEOUS species!
- 5What mnemonic method should you use if you are asked to calculate the value for Kc, given the INITIAL MOLES?Use the ICE method to work out moles at equilibrium, then work out the concentrations of each species, using volume data provided (c = n/v)
Then, you can put the calculated concentrations into the Kc expression to work out Kc! - 6What 3 factors can affect the position of an EQUILIBRIUM? (not Kc or Kp, just the equilibrium)- Changes in temperature
- Changes in concentration/pressure
- The presence of a catalyst - 7Which of the previous factors is the only factor that affects the equilibrium constant?Changes in temperature
- 8Why do changes in concentration have no effect on the equilibrium constant?This is because the rate constants BALANCE OUT
As the products go up, the reactants will balance out
Therefore, it has NO EFFECT on the equilibrium constant - 9Why does the presence of a catalyst have no effect on the equilibrium constant?This is because the rate of the forwards and backwards reaction will increase by the SAME AMOUNT
This means the equilibrium position is UNCHANGED - 10Why do changes in temperature have an effect on the equilibrium constant?Changes in temperature change the rate constants of both the forwards AND reverse reactions, and is therefore likely to change the value of the equilibrium constant
- 11What happens to the value of Kc if the temperature is increased and the forwards reaction is exothermic?The value of Kc will DECREASE
This is because the equilibrium shifts to the left and more reactants form, so, in the Kc expression, you are dividing by a larger value as the denominator will get bigger and this means Kc is SMALLER - 12What happens to the value of Kc if the temperature is increased and the forwards reaction is endothermic?The value of Kc will INCREASE
This is because the equilibrium will shift to the right and more products will form, so, in the Kc expression, you are dividing by a SMALLER value as the numerator will get bigger and this means Kc is BIGGER - 13Is there a relationship between Kc and Kp?Yes, there is a DIRECT RELATIONSHIP between Kc and Kp
- 14What are the equilibrium values expressed as in Kc/Kp?In Kc, the equilibrium values are expressed as CONCENTRATIONS, in mol dm-3
In Kp, the equilibrium values are expressed as PARTIAL PRESSURES - 15What is partial pressure and why is this used in Kc expressions?For reactions involving gases, its difficult to measure the concentration of a particular gas
Instead, the QUANTITY of each gas in an EQUILIBRIUM MIXTURE is described, in terms of the PRESSURE IT EXERTS - its partial pressure (p)
Partial pressure = the contribution that a particular gas makes towards the total pressure - 16Give the formula for calculating the partial pressure of a gasPartial pressure (Pa) = mole fraction x total pressure
- 17What is the formula for calculating a mole fraction?Mole fraction = number of moles in the substance / total number of moles in the gas mixture
- 18What must the sum of all mole fractions in a gas mixture equal?1
(like normal fractions - mole fractions) - 19How is Kp calculated?You work out the value of Kp similarly to Kc, but using partial pressures instead
As with Kc, stoichiometry values in the equations are still used as the POWERS in the expression of Kp - 20Name some suitable units for partial pressureskPa, Pa and atm
You can use any of these units, as long as the SAME UNIT is used for all gases in the kP expression - 21What states does Kp include?Kp only includes GASES, as only gases have partial pressures
So, in Kp, any other species must be IGNORED so ignore any (l), (aq) or (s) - 22What method do you use to work out the units for Kp?The SAME METHOD is used for calculating units for Kc and Kp
With Kc, use moldm-3
With Kp, use Pa, kPa or atm - 23What is the only factor that affects Kp?Both Kp and Kc are only affected by changes in TEMPERATURE
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- A level Chemistry FlashCards sobre Equilibrium chapter 19 flashcards (how far?), criado por Rhea Sekhon em 16-05-2022.
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- Rhea Sekhon
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