Topic 7 - Equilibria Flashcards
What are reversible reactions?
Reactions that can go backwards and forwards.
What is a dynamic equilibrium?
A state where the rate of the forwards reaction equals the rate of the backwards reaction.
Do the concentrations of each substance change in a dynamic equilibrium?
No
What is an assumption about a dynamic equilibrium?
It occurs in a closed system.
What is Le Chatelier’s principle?
If a reaction at equilibrium is subjected to a change in temperature, pressure, or concentration, the position of equilibrium will shift to counteract the change.
If equilibrium shifts to the left, what is produced more?
Reactants.
If equilibrium shifts to the right, what is produced more?
Products.
What is homogenous equilibria?
Where the reactants and the products are in the same state.
What happens when the concentration of a reaction is increased?
Equilibria will shift to decrease the concentration.
What happens when the pressure of a reaction is increased?
Equilibria will shift to decrease the pressure. This means that equilibria will shift to the side will the fewest number of GAS particles.
What happens to a reaction when the temperature is increased?
It shifts to reduce the temperature. It moves in the endothermic direction.
What happens to a reaction when the temperature is decreased?
It moves in the exothermic direction.
How do catalysts affect the position of equilibrium?
They have no effect on the position of equilibrium.
What effect do catalysts have on the rate of reaction?
They will speed up the forwards and backwards reactions equally.
What is Kc?
The equilibrium constant in relation to concentration.
What symbol represents ‘concentration of something’?
Square brackets. [C].
What goes on the top and the bottom for the Kc equation?
Products on the top and reactants on the bottom.
How do the molar values in the balanced equation affect the Kc equation?
The molar values (big numbers in front of the molecules) are the powers of the concentrations in the Kc equation.
Which states of matter are not included in the Kc expression?
Solids and pure liquids.
Why aren’t solids and pure liquids included in the Kc equation?
Their concentration is constant.
Can molar concentrations be used to find Kc?
Yes
What does the acronym ICE stand for?
Initial
Change
Equilibrium
What is the formula for moles?
Mass/Mr
How many moles of products are there at the start of a reaction?
0
What is the formula for concentration?
mol/volume
Will a change in temperature change the value of Kc?
Yes
If temperature change causes equilibrium to shift to the right, what direction does Kc go?
Increase
If temperature change causes equilibrium to shift to the left, what direction does Kc go?
Decrease
Will a change in concentration change the value of Kc?
No
Will adding a catalyst change the value of Kc?
No
What is total pressure?
The sum of all the pressures of the individual gases (partial pressures).
How is the partial pressure of a gas calculated?
Through mole fractions.
What is a mole fraction?
The proportion of a gas in a gas mixture.
What is the equation for a mole fraction?
Mole fraction = no. of moles of gas/total no. of moles in the gas mixture
What is the equation for partial pressure?
Partial pressure = mole fraction of gas x total pressure in mixture
What is Kp?
The gas equilibrium constant (with pressure).
What is used instead of concentrations in a Kp equation?
Partial pressures.
What does the Haber Process produce?
Ammonia (NH3).
What is the Haber Process reaction?
N2(g) + 3H2(g) –> 2NH3(g)
delta H = -92kJmol^-1
What pressure does the Haber Process take place at?
200atm.
What temperature does the Haber Process take place at?
400*C
Why does the Haber Process take place at 200atm and 400*C?
So that the pressure is high enough to produce a good yield without being too expensive or dangerous.
The temperature needed to be high enough that the reaction isn’t too slow, but if the temp. is too high, then the yield will be lower because it is an endothermic reaction.
What does the Contact Process make?
Sulfuric acid. (H2SO4)
What is the Contact Process reaction?
2SO2 + O2 —> 2SO3
What catalyst is used in the Contact Process?
V2O5
Vanadium (V) Oxide
Is the Contact Process endothermic or exothermic?
Endothermic
What is the Bronsted-Lowry definition for an acid?
A proton donor.
What is created when an acid dissolves in water?
A hydroxonium ion H3O^+.
Often represented as H^+.
This makes the solution acidic.
What is the Bronsted-Lowry definition for a base?
A proton acceptor.
What is released when a base reacts with water?
Hydroxide (OH-) ions.
What is a strong acid/base?
One that dissociates almost completely into its ions in solution.
What is a weak acid/base?
One that dissociates partially/poorly into its ions in solution.
What is an example of a weak acid?
CH3COOH (ethanoic acid).
What are three examples of strong acids?
HCl (hydrochloric acid)
HNO3 (nitric acid)
H2SO4 (sulfuric acid)
What are two examples of strong bases?
KOH (potassium hydroxide)
NaOH (sodium hydroxide)
What is an example of a weak base?
NH3 (ammonia)
What is a conjugate acid?
A species that has gained a proton.
What is a conjugate base?
A species that has lost a proton.
What do an acid and a base react together to produce?
A neutral salt and neutral H2O.
What are salts made from in an acid-base reaction?
The metal from the base (or ammonium ion) and the non-metal (other than the H) from the acid.
What is different about Ammonia reactions with acids?
No water is produced.
What is the equivalence point or end point in a titration curve?
The point where the acid has been fully neutralized by the base. There is a sharp vertical that shows the rapid change in pH.
What sort of indicator do you need to use in a titration reaction?
One that changes color entirely within the vertical (end point).
What are 2 indicators?
Phenolphthalein and Methyl Orange.
