Physical Unit 1.6: Equilibria Flashcards
what happens at dynamic equilibrium?
forward & reverse reactions happen at equal rates
concentrations of reactants & products remain constant
what is a closed system?
one where no substances can enter or exit
what is Le Chatelier’s principle?
if the conditions of a reaction at equilibrium are changed, then the position of equilibrium moves to oppose that change
what is the effect of a catalyst on the position of equilibrium?
no effect
the catalyst increases the rate of the forward & reverse reaction equally
equilibrium reached faster
what is the effect of increasing & decreasing temperature on the position of equilibrium?
increasing: equilibrium position shifts to oppose the increase in temperature so shifts in endothermic direction (L or R)
decreasing: equilibrium position shifts to oppose the decrease in temperature so shifts in the exothermic direction (L or R)
what is the effect of increasing & decreasing pressure on the position of equilibrium?
increasing: equilibrium position shifts to oppose the increase in pressure so shifts to the side with fewer gas molecules (L or R)
decreasing: equilibrium position shifts to oppose the decrease in pressure to shifts to the side with more gas molecules (L or R)
what is the effect of increasing & decreasing concentration on the position of equilibrium?
increasing: equilibrium position shifts to oppose the increase in conc. so shifts in the direction to use up the added substance (L or R)
decreasing: equilibrium position shifts to oppose the decrease in conc. so shift in the direction to create more of the substance that is removed (L or R)
what is the formula, temperature, pressure & catalyst used in the Haber process?
450C
200atm
iron
why is a compromise temperature used?
lower temperature gives higher yield of NH3 bc forward reaction is exothermic
increasing temp. increases rate of reaction
so 450C is a compromise b/w yield & rate
why is a compromise pressure used?
increasing pressure increases yield of NH3 bc there are fewer gas moles on the right side
but high pressure is v expensive (pipes & energy cost)
so 200atm is a compromise b/w yield & cost
why is an iron catalyst used?
catalyst increases rate of reaction but has no effect on yield
what is Kc?
equilibrium constant
‘how far the position of equilibrium wants to sit in b/w the sides’
what is Kc affected by?
temperature only
NOT pressure, conc. or catalyst
what is the formula for Kc?
concs of products at equilibrium/concs of reactants at equilibrium
raised to the power of big #s
the higher the Kc…
the further right the equilibrium is
