11th2nd APCHEM: Chemical Thermodynamics

Entropy … when delta S is positive and … when delta S is negative

increases, decreases

Why does entropy tend to increase with increasing temperature?

molecules move quicker, increasing randomness

Why does entropy tend to increase with increasing volume (pertains to gas molecules)

a bigger volume means there are more possible positions for molecules to occupy

How does the number of independently moving molecules affect entropy? (mostly relevant to gas molecules)

a greater amount of molecules means more space is occupied

Name one difference between standard entropies and heat of formation

Standard entropies of elements in their standard state are NOT 0

∆S of a reaction equation

standard entropies of products multiplied by their coefficients minus standard entropies of reactants multiplied by their coefficients

What is Gibbs Free Energy?

the energy available in a system to do work

Positive delta G indicates a … reaction, while negative delta G indicates a … reaction

non-spontaneous, spontaneous

Gibbs Free Energy equation (naught), given ∆H(˚) and ∆S(˚)

∆G(˚) = ∆H(˚) - T∆S(˚)

What does naught, ˚, mean?

at STP, meaning all pressures of species in the reaction are 1 atm or all concentrations of species in the reaction are 1M

How to find delta G from delta G˚

∆G = ∆G˚ + RTln(Q)

At equilibrium, ∆G = 0, so the equation involving ∆G˚ can be rewritten as..

0 = ∆G˚ + RTlnK

∆G˚ = -RTlnK

Based on the equation ∆G˚ = -RTlnK, the sign before delta G naught depends on

the argument of K

Temperature dependencies of ∆G˚, ∆S˚, and ∆H˚?

delta S naught and delta H naught are both temperature independent, while delta G naught IS temperature dependent

temperature requirements of Gibbs Free Energy equation

must be Kelvin and at least zero

If both the delta H term and ∆S term are positive, then how does temperature determine delta G?

the higher the temperature, the more delta H has to subtract, meaning higher temperature leads to lower delta G

If both the delta H term and delta S term are negative, then how does temperature determine delta G?

the new sign of T∆S is positive, meaning a higher temperature leads to a higher delta G