Chem entropy/spontaneity

Entropy (S) def

A measure of the dispersal or distribution of matter/energy

When moving to more disorder (s→g), does entropy increase or decrease?

Increase (positive change)

Does solid, gas, or liquid have the most entropy?

Gas

When explaining changes in entropy, what 2 things should you talk about?

1. Changes in state (s, l, aq, g)

2. Number of moles (of stuff in each state)

What’s the 2nd law of thermodynamics?

Spontaneous processes always occur with an increase in the entropy of the universe.

Absolute entropy def

Entropy under standard temperature and pressure conditions

What’s the equation for calculating ΔS^Ɵ using standard entropy values?

ΔS^⊝ = ΣS^⊝_(products) - ΣS^⊝_(reactants)

Gibbs energy (G) def

The energy produced by a system that can be used to do work - the energy left over after the heat energy (enthalpy) is used to disperse particles (entropy)

What does it mean if the ΔG is negative?

The reaction is spontaneous

What’s the equation for calculating ΔG using Gibbs energy of formation values?

ΔG^⊝ = ΣΔG_f^⊝_(products) - ΣΔG_f^⊝_(reactants)

Using ΔG (system) = ΔH (system) - TΔS (system), what determines the sign of ΔG when the temperature is low?

Sign of the enthalpy change - T is basically zero so entropy change doesn’t matter bc that whole thing is zero. So, if exothermic (-H) then G is negative/spontaneous and if endothermic (+H) then G is positive/not spontaneous

A

A