Module 5: Equilibrium and Acid Reactions Flashcards
What is entropy?
It is the measure of number of possible arrangements of a system
When can entropy increase?
When the volume increase, number of particles increases, temperature increases or there is a change in state
What is a spontaneous reaction?
Is a reaction that occurs on its own accord
When is a reaction spontaneous?
ΔG < 0
When is a reaction not spontaneous?
ΔG > 0
When is a reaction at equilibrium?
ΔG = 0
How do you calculate gibbs free energy?
ΔG = ΔH - TΔS
When is a reaction always spontaneous according to S and H?
ΔH < 0 (Exothermic) and TΔS > 0 (increase in entropy)
When is a reaction never spontaneous according to S and H?
ΔH > 0 (Endothermic) and TΔS < 0 (decrease in entropy)
When is a reaction spontaneous at high temperatures according to S and H?
ΔH > 0 (Endothermic) and TΔS > 0 (increase in entropy)
When is a reaction spontaneous at low temperatures according to S and H?
ΔH < 0 (Exothermic) and TΔS < 0 (decrease in entropy)
What are irreversible reactions?
Are reactions which occur in one direction
What are some examples of irreversible reactions?
Baking a cake
Combustion reactions
Combustion of magnesium and iron wool
What are reversible reactions?
Are reactions where the products formed can react again and reform the reactants
What are some examples of reversible reactions?
Evaporation and condensation of water
Formation of saturated sugar solution
Reaction between de/hydrated cobalt (II) chloride
Reaction between iron (III) nitrate and potassium thiocyanate
When is equilibrium reached in the evaporation and condensation of water?
When the rate of evaporation is equal to the rate of condensation
What colour is dehydrated cobalt (II) chloride?
Blue
What colour is hydrated cobalt (II) chloride?
Pink
What colour is a solution of iron (III) nitrate?
Pale yellow
What colour is a solution of potassium thiocyanate?
Colourless
What colour is iron (III) thiocyanate?
Deep red
What is chemical equilibrium?
When both reactants and products are in concentrations which have no further tendency to change with time
What is dynamic equilibrium?
When the rate of forward reaction and the rate of reverse reaction is equal
What is the Haber process?
The production of ammonia from hydrogen gas and nitrogen gas
What is the extent of a reaction?
It is how much product has been formed when equilibrium is met
What are the three factors which affect collision theory?
- Frequency of collisions
- Orientation of the particles
- Whether there is sufficient energy to break chemical bonds
What is static equilibrium?
When the rate of forward reaction and reverse reaction is almost zero
What is an example of static equilibrium?
carbon (graphite) <—-> carbon (diamond)
What are non-equilibrium systems?
Reactions that never reach an equilibrium and are irreversible
What are some examples of non-equilibrium systems?
Combustion and photosynthesis
What is Le Chatelier’s principle?
If an equilibrium system is subjected to a change or disturbance in conditions, the system will adjust itself to counteract and minimise the effect of change
How does increase in concentration of reactants impact equilibrium?
Forward reaction is favoured, equilibrium shifts to the right
How does increase in concentration of products impact equilibrium?
Reverse reaction is favoured, equilibrium shifts to the left
How does increase in pressure impact equilibrium?
Causes the equilibrium to shift towards the direction with less number of moles
How does decrease in pressure impact equilibrium?
Causes the equilibrium to shift towards the direction with more number of moles
How does decrease in volume impact equilibrium?
(Increases pressure) Causes the equilibrium to shift towards the direction with less number of moles
How does increase in volume impact equilibrium?
(Decrease pressure) Causes the equilibrium to shift towards the direction with more number of moles
When is a reaction exothermic?
ΔH = -ve
Which side is the energy on for exothermic reactions?
Product side
When is a reaction endothermic?
ΔH = +ve
Which side is the energy on for endothermic reactions?
Reactant side
How does increase of temperature impact equilibrium?
Causes the equilibrium to shift towards the direction which does not produce energy to use up the extra energy
How does decrease of temperature impact equilibrium?
Causes the equilibrium to shift towards the direction which produces energy to make up for the lost energy
What does a rate vs time graph look like?
Forward rate decreases, reverse rate increases until they meet in the middle
What does an amount vs time graph look like?
Reactants and products increase and decrease until they are both straight lines
What does a sharp peak on one chemical mean on a concentration equilibrium graph?
Change in concentrations
What does a sharp peak of all chemicals mean on a concentration equilibrium graph?
Change in pressure or volume
What does a smooth peak of all chemicals mean on a concentration equilibrium graph?
Change in temperature
How do you remember the equilibrium constant equation?
PORK
product over reactant = Keq
What is the symbol of equilibrium constant?
Keq
What does the Keq indicate?
The equilibrium position
What does it mean if the Keq is greater than 1?
Equilibrium tends towards the products (right)
What does it mean if the Keq is smaller than 1?
Equilibrium tends towards the reactants (left)
What does it mean if the Keq is very large?
The reaction is near completion
What does it mean if the Keq very small?
The forward reaction hardly occurs
What is the only thing that can impact Keq?
Temperature
When is the Keq accurate?
When a system is at equilibrium
What is reaction quotient?
When the equilibrium expression is different to Keq
What is the symbol for the reaction quotient?
Q
What reaction favoured if Q>Keq?
The reverse reaction
What reaction favoured if Q<Keq?
The forward reaction
What reaction favoured if Q=Keq?
The system is at equilibrium
What are the only things considered when calculating Q?
Gases and aqueous solutions
How does an increase of temp impact Keq of endothermic reactions?
Favours forward reaction hence Keq value increases
How does a decrease of temp impact Keq of endothermic reactions?
Favours reverse reaction hence Keq value decreases
How does an increase of temp impact Keq of exothermic reactions?
Favours reverse reaction hence Keq value decreases
How does a decrease of temp impact Keq of an exothermic reactions?
Favours forward reaction hence Keq value increases
What is the structure of water?
2 hydrogen bonds covalently bond to an oxygen atom
Are the covalent bonds in water polar or non-polar?
Polar
What bonds exist between water molecules?
Hydrogen bonds
When is a substance soluble?
When more than 0.1 mol of it will dissolve in 1L of water at 25*C
When is a substance insoluble?
When less than 0.01 mol of it will dissolve in 1L of water at 25*C
When is a substance slightly soluble?
When 0.01-0.1 mol of it will dissolve in 1L of water at 25*C
What does SNAAP stand for?
Sodium
Nitrate
Ammonium
Acetate
Potassium
What are the SNAAP salts?
Salts which are soluble
What is the solubility product?
Is the product of the concentration of ions in a saturated solution of a insoluble salt
What does Ksp include?
Only aqueous solutions
What is the ionic product?
The product of the concentration of ions in any solution
When is a solution saturated?
When the ionic product = Ksp
How does Ksp show solubility?
The bigger the Ksp the more soluble it is
When will a precipitate not form?
Ionic product < Ksp
When will a precipitate form?
Ionic product > Ksp
Why is the undissolved solid not included in the Ksp calculation?
As it remains constant and there is no change in concentration
What is Kc?
It is like the Keq
What happens to the Kc when all moles are halved, doubled, tripled etc?
Kc to the power of what happened
eg if halved Kc to the power of half
What happens to the Kc when the reaction is reversed?
It will be Kc to the power of a negative
What is Kp and how do you calculate it?
It is the equilibrium constant based on pressure and it is calculated the same way as Keq but with the pressures
How to calculate Ksp from molar solubility?
- Write balanced equation A ⇌ B + C
- Ksp = [B][C]
- Substitute molar solubility in and if required multiply by the number of ions produced
What is a homogeneous equilibrium?
Is a reaction where all of the products and reactants are the same state
What is a heterogeneous equilibrium?
Is when there are different states in the reaction
Is the self-ionisation of water exothermic of endothermic?
Endothermic
How do you find concentration from Ksp?
Use a rice table and solve for x
Is the statement [H3O+] = [OH-] always true?
Yes at all temperatures pure water will always have [H3O+] = [OH-]
How does the addition of a catalyst affect a reversible reaction?
It decreases the activation energy of both the forward and reverse reaction
