Topic 8: Extent of chemical reactions Flashcards
What are the 2 types of system?
Open and close
What is an open system?
matter and energy can be exchanged with the surroundings
What is a closed system?
Only exchanges energy with the surroundings
What happens in an equilibrium reaction?
both forward and reverse reactions occur simultaneously, rate of both reactions are equal
What is equilibrium?
The rate of the forward reaction equals the rate of the reverse reaction. AKA no net change of concentration of reactants and products
What happens during dynamic equilibrium?
- The amt of concentrations (colour intensity) of chemical substances remain constant
- total gas pressure is constant
- temp is constant
- the reaction is incomplete (all subtsances are present in the equilibrium mixture)
What can a chemical reaction be regarded as?
An system, everything else around it is the surroundings
Significant of numerical size of Kc?
- > 10^4, favours the forward reaction (more products are made)
- 10^-4<Kc<10^4, both sides are favoured to some extent
- <10^-4, favours the reverse reaction (more reactants are made)
What is Kc?
- equilibrium constant
- reciprocal if the equation is reversed
- squared if the coefficients are doubled
- rooted if the coefficients are halved
- indicate the ratio of products/reactants at euilibrium
What is Qc/CF
- reaction quotient/ concentration factor
- the quantity that changes as a reaction system approaches equilibrium
- indicate the ratio of products to reactants
What does decreasing the volume of the container do to the pressure of the gases in an equilibrium mixture?
increase pressure
What does increasing the volume of the container do to the pressure of the gases in an equilibrium mixture?
decrease pressure
What does LCP do when there’s an increase in volume of the container in an equilibrium mixture?
shift to the side with more mole
What does LCP do when there’s a decrease in volume of the container in an equilibrium mixture?
shift to the side with less mole
What does LCP do when there’s an increase/decrease in volume of the container in an equilibrium mixture but the moles on both sides are equal?
no shift to the position of equilibrium. AKA doesn’t affect the equilibrium
What does LCP do to increase the concentration of aqueous species?
shift to the side with greater number of moles
What does LCP do to decrease the concentration of aqueous species
shift to the side with fewer moles
what happens when you increase the temperature? (exothermic reactions)
- equilibrium shifts backwards/ left
- tries to absorb the heat so the backward reaction is favoured cus it’s endothermic
- K decreases
what happens when you decrease the temperature? (exothermic reactions)
- equilibrium shifts forward/right
- tries to replace some of the heat that’s removed so the forward reaction is favoured cus it’s exothermic
- K increases
what happens when you increase the temperature? (endothermic reactions)
- favour the forward reaction cus it’s endothermic
- shifts to the right/forward
- K increases
what happens when you decrease the temperature? (endothermic reactions)
- favour the backward reaction cus it’s exothermic
- shifts to the left/backwards
- K decreases
If Qc ≠ Kc, what happens to the system?
- not at equilibrium, some change must be made to PARTIALLY OPPOSE the change
How do catalyst increase ROR whilst being “green”?
- Provides an alternative pathway with lower Ea
- Don’t require additional heat (energy) which could be used to increase ROR
