Dynamic equilibrium
When the forward and reverse reaction are occurring at the same rate/speed (and the concentration of R/P stops changing)
Equilibrium constant (๐ฆ)
The ratio of the concentration of the R/P at equilibrium
Law of mass action (equation for ๐ฆ)
๐ฆ = (Cc ยท Dd) รท (Aa ยท Bb)
- Letters are the concentrations of the substances (in M)
- Superscripts are the coefficients of the substances
When the value of ๐ฆ is large (๐ฆ >> 1)...
Concentration of products is bigger than the concentration of reactants (right side favored)
When the value of ๐ฆ is small (๐ฆ << 1)...
Concentration of reactants is bigger than the concentration of products (left side favored)
For gaseous only reactions, the ___ of a gas is = ___ and can be expressed using ___ (what equation)
๐ฆp = (PcC ยท PdD) รท (PaA ยท PbB)
- The partial pressure of a gas is = its concentration
Equation(s) for converting between ๐ฆc โ ๐ฆp (only for gases behaving ideally)
๐ฆp = ๐ฆc ยท (RTฮn) โ ๐ฆc = ๐ฆp รท (RTฮn)
- ๐ฆp = partial pressure of reaction
- ๐ฆc = concentration equilibrium of reaction
- ฮn = (coefficients of all products) - (coefficients of all reactants)
- R = 0.08206 L ยท atm / mol ยท K
If you reverse an equation, the equilibrium constant is...
Inverted (1 รท ๐ฆforward)
If you multiply an equation, the equilibrium constant is...
Raised to the same factor (๐ฆx)
If you add equations to find the overall ๐ฆ, the equilibrium constants are...
Multiplied by each other (๐ฆ1 ยท ๐ฆ2)
Solid (s) and pure liquid (l) substances don't change their ___, so in equilibrium expressions they can be ___
1) Concentrations
2) In equilibrium expressions they can be omitted entirely (they do not effect the equilibrium state)
Reaction quotient (๐ธ)
The ratio of the concentrations of the R/P at any point in the reaction
- Same concentration and partial pressure equations as๐ฆ
If ๐ธ > ๐ฆ, the reaction moves ___ to reach equilibrium
Right (more products are made)
If ๐ธ < ๐ฆ, the reaction moves ___ to reach equilibrium
Left (more reactants are made)
If ๐ธ = ๐ฆ, the reaction is ___
At equilibrium
If you increase the concentration of reactants (L < ๐ฆ), the reaction shifts ___
To the right to form more products
(decrease in concentration shifts left to form more reactants)
If you increase the concentration of products (L > ๐ฆ), the reaction shifts ___
To the left to form more reactants
(decrease in concentration shifts right to form more products)
If the volume of a reaction (at equilibrium) increases, the pressure ___
If the volume decreases, the pressure ___
1) Volume increase โ pressure decreases
2) Volume decreases โ pressure increases
If you increase the pressure of a reaction, the reaction shifts ___ in order to ___ the pressure
1) Shifts to the side with less moles of gas
2) decrease the pressure (return to equilibrium)
If you decrease the pressure of a reaction, the reaction shifts ___ in order to ___ the pressure
1) Shifts to the side with more moles of gas
2) Increase the pressure (return to equilibrium)
Equation for finding the concentration of a substance
C = n รท V
- n = moles of substance
- V = volume given
If you add a noble gas to a reaction, the pressure ___ but the volume ___, the value of Q ___
1) Pressure increases
2) Volume stays the same
3) The value of Q stays the same
If you change the temperature of a reaction what happens to ๐ฆ
The actual value of ๐ฆ changes because the equilibrium constant is temperature dependent
Exothermic reaction vs. endothermic reaction (in relation to heat)
- Exothermic reactions RELEASE heat (heat is a product)
- Endothermic reactions ABSORB heat (heat is a reactant)
In exothermic reactions, what direction does the reaction shift and what happens to the value of ๐ฆ when you increase or decrease the temperature
1) Increase temp (add heat product) โ shifts left to reactants โ ๐ฆ decreases
2) Decrease temp (remove heat product) โ shifts right to products โ ๐ฆ increases
In endothermic reactions, what direction does the reaction shift and what happens to the value of ๐ฆ when you increase or decrease the temperature
1) Increase temp (add heat reactants) โ shifts right to products โ ๐ฆ increases
2) Decrease temp (remove heat reactants) โ shifts left to reactants โ ๐ฆ decreases
Equation for finding ฮG for a reaction under any conditions
ฮG = (-RT) ยท ln(๐ฆ)
- R = 8.314 J/K
Equation for equilibrium constant using ฮG
๐ฆ = e(-ฮG รท RT)
- ฮG is the one found from a previous reaction using 'ฮG under any conditions' equation
Find ๐ธp of a reaction when given moles of substances and volume
1) Find partial pressure of substances using P = nRT รท V
2) Plug those values into regular reaction quotient equation