chemistry year 12 term 1

Dynamic equilibirum

a state in a reversible reaction where the forward reaction and the reverse reaction happen at the exact same rate

Static equilibrium

a state where a chemical reaction has completely stopped, and the rates of both the forward and reverse reactions equal zero

conditions required for dynamic equilibirum

• closed system

• reversible reaction

• equal rates and constant concentration

• constant macroscopic qualities (eg, colour)

closed system

• not open to atmosphere

• energy can be exchanged

• no gain or loss in mass

open system

• open to atmosphere

• can exchange energy

• can gain or lose mass

Enthalpy: ΔH

• amount of heat evolved or absorbed in a reaction carried out at constant pressure

• (energy to break reactant bonds) - (energy released from product bonds)

Entropy: ΔS

Measure of the dispersal of energy

• solid —> liquid —> gas

• (products) - (reactants)

Gibbs free energy ΔG = ΔH - TΔS

ΔG negative = spontaneous

ΔG positive = non spontaneous

ΔH>0, ΔS >0

spont at high temp, not at low temp

ΔH<0, ΔS>0

spont at any temp

ΔH<0, ΔS<0

spont at low temp, not at hot temp

ΔH>0, ΔS<0,

spont at no temp

ΔG=0

equilibrium

Photosynthesis:

• endo

• always non spontaneous at room temp

Define LCP

any change imposed on a system at EQ will cause system to shift to minimise the disturbance (PARTIALLY counteract)

LCP questionformula

1. Identify disturbance

2. According to LCP, system shifts ____

3. To side with less/more/exo/endo to minimise disturbance

4. Describe effect on concentration, rate or forward reverse, colour etc.

What spikes up a conc time graph

• adding a reactant

• changing volume/pressure

What makes conc graph suddenly drop

removing product/reactant

• SOLID ISN’T AFFECTED

change in conc is always in

change in conc is always in

Why are redox rxn not eq?

they are reversible but no EQ since e- can’t flow both ways

partial pressure

the pressure that each gas exerts on surroundings

Does adding inert gas at constant volume effect equilibrium

no effect

Adding inert gas at constant pressure — does it effect eq

no

What happens to graph when temp increases

lines have gradual increase

Effect of catalyst on system

• both reverse and forward reactions increase in rate, but at same increments

• equilibrium stays the same

Causes of sudden drop in conc graph

• dilution

• taking product/reactant out

• increase volume

Common things that are soluable

• nitrates

• potassium

• sodium

• ammonium