Thermodynamics Part 1

Spontaneous reactions:

• NO continuous WHAT assistance is required 

• May require a “WHAT” but self sufficient after 

• Not necessarily an WHAT reaction (can be slow but spontaneous) 

• Can be WHAT or WHAT 

Spontaneous reactions:

• NO continuous EXTERNAL assistance is required 

• May require a “JUMP START” but self sufficient after 

• Not necessarily an INSTANTANEOUS reaction (can be slow but spontaneous) 

• Can be EXOTHERMIC or ENDOTHERMIC 

Non-spontaneous process

• Products can still be obtained but continuous WHAT assistance is requires

Non-spontaneous process

• Products can still be obtained but continuous EXTERNAL assistance is required (boiling water - applying heat)

• If the forward direction is SPONTANEOUS, the reverse reaction is WHAT

• If the reverse direction is SPONTANEOUS, the forward reaction is WHAT

• If the forward direction is SPONTANEOUS, the reverse reaction is NON-SPONTANEOUS

• If the reverse direction is SPONTANEOUS, the forward reaction is NON-SPONTANEOUS

Gibb’s free energy (G)

• A property thats analogous to WHAT in chemical system 

• If spontaneous ΔG WHAT 0KJ 

• At equilibrium ΔG WHAT 0KJ

• Non-spontaneous ΔG WHAT 0KJ

Gibb’s free energy (G)

• A property thats analogous to POTENTIAL ENERGY in chemical system 

• If spontaneous ΔG < 0KJ 

• At equilibrium ΔG = 0KJ

• Non-spontaneous ΔG > 0KJ

How to determine Gibb’s free energy

ΔG = ΔrH - TΔS

Entropy (S)

• A measure of WHAT or WHAT in a system resulting from the dispersal of WHAT and/or WHAT

• Units = WHAT

• The more disordered the system → The WHAT the entropy

Entropy (S)

• A measure of RANDOMNESS or DISPERSAL in a system resulting from the dispersal of MATTER and/or ENERGY

• Units = J/molK

• The more disordered the system → The LARGER the entropy

Entropy of the universe is always WHAT 

Entropy of the universe is always INCREASING  

What is the equation for entropy

ΔrS = ∑nPΔPS - ∑nRΔRS

ΔS > 0 = WHAT

ΔS = 0 = WHAT

ΔS < 0 = WHAT

ΔS > 0 = Spontaneous

ΔS = 0 = Equilibrium

ΔS < 0 = Non-spontaneous

Equation for the spontaneity of a reaction

ΔGrxn = ΔrHrxn - TΔSrxn

What affects the spontaneity of a given reaction:

1. ΔS and ΔH vary very slightly with WHAT → independent of WHAT 

2. ΔG is strongly WHAT on temp

What affects the spontaneity of a given reaction:

1. ΔS and ΔH vary very slightly with TEMP → independent of TEMP 

2. ΔG is strongly DEPENDENT on temp

ΔH = negative

ΔS = Positive

ΔG = WHAT

ΔH = negative

ΔS = Positive

ΔG = <0 at all temperature → SPONTANEOUS at all temperatures

ΔH = Positive

ΔS = Negative 

ΔG = WHAT

ΔH = Positive

ΔS = Negative 

ΔG = >0 at all temps → NON-SPONTANEOUS at all temperatures

ΔH = Negative 

ΔS = Negative 

ΔG = WHAT

ΔH = Negative 

ΔS = Negative 

ΔG = Change from NEGATIVE to POSITIVE when temp increases (T>ΔH/ΔS) → Only spontaneous at LOW temperature 

ΔH = Positive 

ΔS = Positive 

ΔG = WHAT

ΔH = Positive 

ΔS = Positive 

ΔG = Change from POSITIVE to NEGATIVE when temp increases (T>ΔH/ΔS) → Only spontaneous at HIGH temperature 

Third law of thermodynamics:

• The entropies of all perfect WHAT substances are the same at T = WHAT

• At absolute zero all the substances have no WHAT 

• This means that a system will have perfect order at T= 0K → ΔS = WHAT

Third law of thermodynamics:

• The entropies of all perfect CRYSTALLINE substances are the same at T = 0K

• At absolute zero all the substances have no KINETIC ENERGY 

• This means that a system will have perfect order at T= 0K → ΔS = 0

Which factors can affect the entropy of the system:

• WHAT

• WHAT

• WHAT

• WHAT

Which factors can affect the entropy of the system:

• Physical state

• Temperature

• Number of particles in the sample

• Complexity and size of molecules  

Large increase in entropy = WHAT

Large increase in entropy = PHASE CHANGE

Number of particles in the sample

• Less particles → WHAT → WHAT

• More particles → WHAT → WHAT

• Solid particles dissolve in H2O → freedom in WHAT → Increase in WHAT  

• Additional WHAT/WHAT in a mixture 

Number of particles in the sample

• Less particles → Less disorder → smaller

• More particles → More disorder → Larger

• Solid particles dissolve in H2O → freedom in MOVEMENT → Increase in S  

• Additional ORIENTATION/INTERACTION in a mixture 

Complexity and size of molecules  

• WHAT molecules have higher S → more WHAT → Randomness is through WHAT and WHAT within the molecule 

Complexity and size of molecules  

• LARGER molecules have higher S → more ATOMS → Randomness is through VIBRATION and ROTATION within the molecule 

Change in the concentration use din a reaction

WHAT equation for Q

WHAT equation for K

Change in the concentration use din a reaction

ΔGrxn = ΔG°rxn + RTln(Q) equation for Q

ΔG°rxn = -RTln(Q) equation for K → ΔGrxn = 0