Year 2 - A level Flashcards
What is needed for a dynamic equilibrium?
-Closed system, forward and backward reactions have same rate, conc. of products and reactions always constant(not equal)
What is Le Chatilier’s principle?
When a change is applied to a system in dynamic equilibrium, the system shifts to oppose the change.
What 4 things affect equilibrium?
- Temp. warmer shifts to endothermic
- Conc.
- Pressure
- Catalysts (no shift just rate increase)
Conditions for Haber process?
450C at 200atm - compromise conditions with Iron catalyst
Conditions for Hydration of ethene?
570k - compromise, 6000-7000kPa - high is good. Lots of steam not much ethene (cheaper)
Conditions for methanol formation?
520k, 5000-10000kPa, catalyst copper, zinc oxide and aluminium oxide.
Kc equation for aA + bB ⇌ cC dD
kc = [C]^c[D]^d/[A]^a[B]^b. If kc>1 eq lies to right as [Products]>[Reactants]
Equation for partial pressure of a gas?
P(A) = no moles A/total moles x total pressure
Kp equation for aA + bB ⇌ cC dD when gases
p(C)^c p(D)^d/p(A)^a p(B)^b
What acronym do you use when working out moles in equilibrium?
ICE - initial , change , equilibrium
What equation links ΔStotal, R and k?
ΔStotal = Rlnk when k is small, S is negative(unfeasible)
What equation links ΔG, R, T and k?
ΔG = -RTlnk
What is a Bronsted-Lowrey base?
A proton acceptor
What is a Bronsted-Lowrey acid
A proton donor
What does mono, di and tri-protic mean?
How many moles of protons per mole of acid.
What makes an acid stronger?
More dissociation
What is key about weak acids?
They only partially dissociate
Equation for PH?
PH = -log10[H+]
Equation for [H+] from PH?
[H+] = 10^-PH
Ka equation for weak acids?
Ka = [H+][A-]/[HA] as [H+] = [A-] in weak also Ka = [H+]^2/[HA]
Equation for pKa?
pKa = -log10Ka
Equation for Kw?
Kw = [H+][OH-] = 1x10^-14
Equation for pKw?
pKw = -log10Kw
What is a buffer solution?
One that can oppose change in PH when small quatities of acid or alkali are added.
Rearrange Ka equation for [H+]
[H+] = √Ka x [HA]
What is enthalpy of neutralisation?
Energy change when one mole of water is formed from acid and base under standard conditions
What indicatiors should be used for combinations of strong/weak acids and strong/weak alkalis?
Both strong/weak - litmus
Strong acid, weak base - Methyl orange
Strong base, weak acid - Phenopthalein
Equation for Kin?
Kin = [H+][In-]/[HIn] at halfway to end point [In-] = [HIn] so [H+] = KIn
On a PH curve when does pKa = PH?
Halfway to the end point(equivalence point) [In-] = [HIn] so they cancel
What are the 2 stages of enthalpy of solution?
-Break up the lattice, hydrate the ions
What is atomisation energy?
Energy change for formation of one mole of gaseous atom from element in standard states.
What is 1st electron affinity?
Energy change for addition of one electron for each mole of atoms in gas phase.
What does Theory vs Experiment show for lattice energy calculations?
Theory assume perfect spheres so difference between two values shows polarisation = covalancey. Big difference more covalent.
