Le Chatelier's Principle Flashcards
Factors effects of temperature, concentration, volume and/or pressure on a system at equilibrium and explain
What is Le Chatelier’s Principle?
(1) For a system at dynamic equilibrium, (2) if a change is made to the condition, (3) the position of the erquilibrium will shift (4) to counteract the change
When should you use Le Chatelier’s Principle?
when predicting how a dynamic equilibrium will respond to change
What is the temperature rule of Le Chatelier’s Principle?
an equilibrium reaction will respond to counteract a change in temperature by shifting to RELEASE ↑ or CONSUME ↓ heat by favouring either the EXOTHERMIC ↑ or ENDOTHERMIC ↓
What do endothermic reactions do?
they consume energy from their surroundings,
What do exothermic reactions do?
they emit or expel heat into their surrondings
Using L.C.P, how will a system respond when the temperature goes up?
the system will try to get rid of heat to lower the temp→ does this by favouring the endothermic reaction → which makes the system cooler by consuming heat
Using L.C.P, how will a system respond when the temperature goes down?
the system will try to get more heat to increase the temp→ does this by favouring the exothermic reaction → which makes the system hotter by emitting heat
Which reaction is favoured to increase the temperature?
the exothermic reaction
Which reaction is favoured to decrease the temperature OR consume heat?
the endothermic reaction
What is nitrogen dioxide?
NO₂ (g)
What is dinitrogen tetroxide?
N₂O⁴ (g)
What is the product and reactant in your nitrogen dioxide and dinitrogen tetroxide
reactant: nitrogen dioxide or 2NO₂
product: dinitrogen tetroxide or N₂O⁴
What is the state of the substances in the 2NO₂ ⇆ N₂O₄ reaction?
gas
What does “the equilibrium shifts to the left” mean?
the equilibrium shifts to the left = the reactants are now predominantly on the left
What does “the equilibrium shifts to the right” mean?
the equilibrium shifts to the right = the reactants are now predominantly on the right
What are the reactants and products when heating cobalt chloride hexahydrate?
reactants: CoCL₂ · 6H₂O (s)
products: CoCl₂ (s) + 6H₂O (g)
What happens to the states in the “heating cobalt chloride hexahydrate” reaction?
goes from solid CRYSTAL reactants to solid and gaseous products
What is the net ionic equation of heating cobalt chloride hexahydrate?
CoCL₂ · 6H₂O(s) ⇆ CoCl₂ (s)+ 6H₂O (g)
What physically and visually happens when you heat cobalt (II) chloride?
the FORWARD or ENDOTHERMIC reaction is favoured → increases the concentration of the hydrated form of cobalt ion → solution turns blue
What physically and visually happens when you cool cobalt (II) chloride?
the REVERSE or EXOTHERMIC reaction is favoured → increases the concentration of the dehydrated form of cobalt ion → solution turns pink.
Is the forward or reverse reaction exothermic in the CoCL₂ · 6H₂O(s) ⇆ CoCl + 6H₂O (g) reaction?
reverse is exothermic
Is the forward or reverse reaction endothermic in the CoCL₂ · 6H₂O(s) ⇆ CoCl + 6H₂O (g) reaction?
forward is endothermic
What colour is the reactant CoCL₂ · 6H₂O(s) (hydrated cobalt chloride)?
pink
What colour is the product CoCl₂ (s) (dehydrated cobalt chloride)
blue
What is the name of CoCL₂ · 6H₂O(s)?
cobalt chloride hetrahydrate
What happens to colours in the CoCL₂ · 6H₂O(s) reaction?
a visual change where the crystals go from pinkish/reddish to blue-ish
What is the net ionic “iron thiocyanite and varying concentrations of ions” reaction?
Fe³⁺ (aq) + 3SCN⁻ (aq) ⇆ Fe(SCN)₃ (aq)
Are the reactants or products favoured at standard conditions in the iron thiocyanate and varying concentrations of ions?
the reactants
What is the colour of Fe(NO₃)₃ (aq) or net ionic-ly Fe³⁺?
yellow
What is the colour of KSCN or net-ionic-ly 3SCN⁻ (aq)?
clear
What is the colour of Fe(SCN)₃?
blood red
What is the state of the reactants and products in the iron thiocyanite reaction?
Fe³⁺+ 3SCN⁻ ⇆ Fe(SCN)₃
What happens if you increase the concentration of a substance using L.C.P?
the equilibrium will shift and the system will start to favour the reaction that uses up the extra/increased substance as a reactant.
What happens if you decrease the concentration of a substance using L.C.P?
the equilibrium will shift and the system will start to favour the reaction that makes the decreased substance as a product.
In what state can you not find the concentration of a substance?
Liquid and solid
If everything in a system is equal, what does changing the amount of a solid substance do to the equilibrium?
nothing. Changing the amount of a solid does not affect the equilibrium
If everything in a system is equal, what does changing the amount of a liquid substance do to the equilibrium?
nothing. Changing the amount of a liquid does not affect the equilibrium
What is the unit of concentration?
moles per litre
How does L.C.P apply to concentration?
if you change the concentration of a reactant or product by ADDING or REMOVING some, the equilibrium will shift to favour the reaction that USES UP or PRODUCES the same reactant or product to return the concentration to normal
What colour is nitrogen dioxide?
brown
What colour is dinitrogen tetroxide?
clear
What are the two ways that pressure can be increased in a system?
1) pumping more gas (of the same concentration) into the system
2) reducing the volume of the system
How can you decrease pressure in a system?
by increasing the volume
The space that gas takes up depends on the number of what?
MOLES.
less moles = less volume = less pressure
more moles = more volume = more pressure
What units is pressure measured in?
kilopascals
What do coefficients have to do with moles?
The coefficients tell you how many moles of the substance are in the reaction. THere are 2 moles of 2NO₂ (g) present and 1 mole of N₂O₄.
What is the net ionic equation of nitrogen dioxide to dinitrogen tetroxide?
2NO₂ (g) ⇆ N₂O₄
What happens when you apply L.C.P to pressure?
an INCREASE or DECREASE in pressure will shift the equilibrium and force the system to favour the reaction that USES UP/CONVERTS the substances with the most moles or PRODUCES the substances with the most moles.
E.g, 2 moles of gas will become 1 mol
What happens if you increase the pressure using L.C.P?
the equilibrium will shift and the system will start to favour the side that uses the higher mole gas as a reactant, converting more moles into less moles
What happens if you decrease the pressure using L.C.P?
the equilibrium will shift and the system will start to favour the side that uses the lower mole gas as a reactant, converting less moles into more moles
Pressure and volume only affect what type of reactants or products?
gaseous
