1.7 simple equilibria and acid-base reactions Flashcards
what is dynamic equilibrium?
when the forward rate of reaction is equal to the reverse rate of reaction
what does the ‘dynamic’ mean in dynamic equilibrium?
what does the ‘equilibrium’ mean?
‘dynamic’ - means that the reaction has not stopped; it is simply moving in both direction at the same rate
‘equilibrium’ - means that the amount of reactants and products (ie conc) in the system is staying the same
what is a closed system?
one from which reactants and products cannot escape
in closed systems, the forward and reverse reactions continue until when?
until dynamic equilibrium is reached
(so all reactions in a closed system are reversible in theory, although theybare onlu considered as such is both forward and reverse reactions occur to a significant extent)
are all reactions in a closwd system reversible?
yes in theory
although they are only considered as such is both forward and reverse reactions occur to a significant extent
what is an open system?
one from which reactants and products can escape
(e.g in a fume cupbord)
why can’t reverse reactions takr place in an open system?
the products are removed as soon as theu are formed, so reverse reactions are not allowed to take place
so these reactions never reach equilibrium, but proceed until all the reactions have been converted into products
if a reaction is represented by an equilibrium sign, what is often assumed?
- the system is closed
- the reverse reaction is significant
what does Le Chatelier’s principle state?
if a chemical system at equilibrium experiences a change in concentration, temperature or pressure, the equilibrium will shift in order to minimize that change
what does le chat’s principle predict?
the direction in whcih the system will move to reestablish equilibrium
what are the 3 factors that can affect the position of equilibrium?
- concentration
- temperature
- pressure (gases only)
le chat’s principle predicts that if a reactant’s concentration in a system is increased, the equilibrium will shift to the ____ in order to decrease the concentration of that reactant
opposite side
e.g H2 (g) + I(g) <-> 2HI (g)
if more hydrogen (or iodine) is added, thr system will move to the ___
right
in order to remove the extra hydrogen
e.g H2 (g) + I(g) <-> 2HI (g)
if iodine is removed, the system will move to the ___
left
to replace the lost iodine
e.g H2 (g) + I(g) <-> 2HI (g)
if hydrogen iodide is added, the system will move to the ___
left
to remove the hydrogen iodide
e.g H2 (g) + I(g) <-> 2HI (g)
if hydrogen iodide is removed, thr system will move to the ___
right
to replace the lost hydrogen iodide
if the forwards reaction is exothermic, then the temperature of the system will rise if the forward reaction takes place. what does this make the reverse reaction?
endothermic, and the temperature of the system will fall if the reverse reaction takes place
le chatelier’s principle predicts that an increase in temperature will favour the (endothermic/exothermic) reaction?
endothermic
le chatelier’s principle predicts that a decrease in temperature will favour the (endothermic/exothermic) reaction?
exothermic
if the ∆H=0, what effect will a change in temperature have on the position of equilibrium?
no effect
2SO2 (g) + O2 (g) ⇌ 2SO3 (g) ∆H=-ve
an increase in temperature will favour the direction which decreases the temperature - ie the (exothermic/endothermic) direction
endothermic
2SO2 (g) + O2 (g) ⇌ 2SO3 (g) ∆H=-ve
(when increasing temperature) as the forwards reaction is exothermic, the reverse reaction must be endothermic, and so the reaction will proceed to the ___?
left
2SO2 (g) + O2 (g) ⇌ 2SO3 (g) ∆H=-ve
a decrease in temperature will favour the exothermic direction, so it can increase the temperature. this is the forward reaction so the reaction will proceed to the ___?
right
what does the pressure in a system depend on?
the number of gas molecules in the system
