Thermodynamics

First Law of Thermodynamics

E is conserved; E cannot be created or destroyed

Second Law of Thermodynamics

spontaneous processes occur in directions that increase overall disorder of the universe

in biochem, define enthalpy.

heat content of our system

entropy (disorder)

A measure of the # of specific ways in which a thermodynamic system can be arranged

Gibbs Free Energy

change in E for a process that combines enthalpy, entropy, and T (assuming constant pressure)

what are the types of systems?

open, closed, and isolated

What does an open system exchange with its surroundings?

matter and energy

What does a closed system exchange with its surroundings?

energy

What does an isolated system exchange with its surroundings?

nothing

change in H

change in enthalpy

change in S

change in entropy

define system

what we are interested in (organism/reaction vessel)

T in the delta G = (delta H) - (T)(delta S)

Temperature in K

define surroundings

everything else (rest of the universe)

How many kj are in a J?

1000 kj

Units for E, heat or w

J = (kg times m²)/s²

Units for work

W = F • d = (m • a) • d = (kg • m²)/s²

equ for K (Kelvin)

K = degree of Celsisu + 273.15

define each variable: delta E = q + w

• change in E by final E - inital E

• q = heat abs. by the sys from surr

• w = work done on the sys from surr

what is the sign of the q when the rxn is exothermic?

exothermic → sys releases heat or heat is given away → negative q

what is the sign of the q when the rxn is endothermic?

endothermic → sys gains heat or heat is taken in → positive q

what is the sign of the w when work is done on the sys?

positive w

what is the sign of the w when work is done by the sys?

negative w

define the variables: delta H = q_p

• delta H = change in enthalpy

• q_p = heat released or taken in at constant pressure

Hess’s Law

Since enthalpy is a state func. meaning it depends only on the initial and final states, we can calculate the total change in enthalpy by summing up all changes.

what are our state func.s?

enthalpy and entropy

how do we know it is a spontaneous rxn based on inequalities?

• delta G < 0 or delta S > (q_p/T)

• when delta E = 0, delta S > 0

define the equation: delta S greater than or equal to (q_p/T)

change in entropy of a reversible process at constant T calculated by the heat transferred at a T

when it is ethalpically favored, but entropically opposed, at what temp is it spontaneous at?

temp below delta H over delta S

when it is ethalpically opposed and entropically favored, at what temp is it spon at?

temp above delta H over delta S