the capacity to do work or to transfer heat

work = force X distance

1 joule = 1 Newton meter = 1 kg m S^-2 = 1 kg m²s^-2

-heat (q) is energy that is transferred as the result of a temperature difference

thermodynamics - the study of work, heat, and the transformation of energy in general

-a system is the area within which a reaction is confined

-everything outside of the system is the surroundings

isolated system - when a system is seale and insulated to prevent any exchange with surroundings (not the case with chemical reactions)

-based on the understanding that energy can neither be created nor destroyed but only changed from one form to another (law of conservation of energy)

E_final - E_initial = ΔE = w + q

*where w+q is the total energy being exchanged with surroundings

-the first law of thermodynamics states that if an amount of heat (q) flows into a system from the surroundings and the surroundings do an amount of work (w) on the system, it will cause the system to have an internal energy change that equals w+q.

-the sum of kinetic and potential energies of all particles in the system

-inetic is related to motion, and potential is related to position

-a state function is any property of a system that depends only on the state of the system, and not on how that state was reached

-the "heat" given out/taken in by exothermic/endothermic reactions. This "heat" is called the enthalpy change and is given by the symbol ΔH

ΔH = total H(products) - total H(reactants)

*there is an enthalpy for every compound

-in an exothermic reaction, the system loses enthalpy

-in an endothermic reaction, the system gains enthalpy

ΔH<0, the reaction is exothermic

 ΔH>0, the reaction is endothermic

*ΔH can be measured experimentally by carrying out the reaction in a calorimeter

standard enthalpies- enthalpy changes measured at a pressure of 1atm and 25C. symbol is ΔH^o

***when a chemicat reaction is carried out at 1atm and 25C, the reactants and products are said to be in their standard states

-bond energy/bond enthalpy are the same thing

-it is the amount of energy required to break or make a bond

**Bond Energy For A Given Bond Does Not Vary From Substance To Substance**

(ie, a C-C bond has the same energy whether in diamond, graphite, or alcohol)

ΔH^o = total BE(products) - totalBE(reactants)

or

ΔH^o  = total BE(bonds broken) - total BE(bonds formed)

-The enthalpy change in a reaction is teh same regardless of the path by which the reaction occurs

-about cancelling out equations and adding/subtracting enthalpies

ΔH_f^o

-is the enthalpy change for the reaction at which the compound is formed from its elements in their most stable standard states

* the standard enthalpy of formation for any element in its most stable standard state is zero.

ΔH^o = totalΔH_f^o_products - totalΔH_f^o_reactants

-essentially, what a ΔH_f^o value tells us is how much chemical energy is stored in a compound

-if the standard enthalpy of formation of a compound is negative, the compound contains less stored energy than the standard states of the elements from which it is formed

-if ΔH_f^o is positive, the compound contains more stored energy than the stanard states of the elements from which it is formed.

***A more stable compound is cemically less reactive***

***A less stable compound is chemically more reactive***

S

-entropy, like enthalpy, is also a state function

-its value depends only on the conditions that determine the state of the system, such as composition, temperature, and pressure

-entropy is a measure of the disorder of the particles (atmos and molecules) that make up the system and the dispersal of energy associated with tehse particles

2nd law:

-In any spontaneous process the total entropy of a system and its surroundings increases.

(in other words, going from order to dsorder is spontaneous... it is natural)

S_final - S_initial = ΔS>0

0itis said that at 0K, the entropy of any pure crystalline substance is zero (no movement, no disorder)

-in general, gases have larger entropies than liquids and liquids have larger entropies than solids

ΔSo = total S^o_products - total S^o_reactants

-a new state function that shows the combined effort of enthalpy and entropy in determining the direction of a reaction is called Gibbs free energy (G)

0at constant temperature and pressure theintricate play between enthalpy and entropy is expressed as:

ΔG =  ΔH - TΔS

When ΔG<0, the reaction is spontaneous

 When ΔG>0, the reaction is not spontaneous

When ΔG=0, the reaction is at equilibrium

The standard free energy change (ΔG^o) for any reaction can be calculated from the standard free energies of formation of reactants and products:

ΔG^o= totalΔG_f^o_products - totalΔG_f^o_reactants

***The relationship between ΔG, the reaction quotien (Q) and the equilibrium constant (K) is defined by ΔG= RTlnQ - RTlnK

*Where R is called gas constant and has the value of 8.14J/K

T is temperature in Kelvin

***A chemical reaction takes place so that the system ends up with less free energy***

-G means the amount of energy a system can spare to do work, or the maximum work obtainabe from a chemical reaction.

w_max = -ΔG

-Ifa chemical reaction is not spontaneous in the desired direction, delta G provides us with the estimation as to how much minimum amount of work needs to be done to make the reaction proceed as desired.

-since ΔG is a state function just like ΔH, we can apply Hess's law to obtain an overall ΔG (as we do for ΔH overall)

-when this idea is applied to drive a reaction, that is, to make a nonspontaneous reaction go by combining the reaction with another reaction that has a greater and negative ΔG (so that overall ΔG<0), the strategy is called reaction coupling.

-bond order indicates how many electrons are involved in holding a pair/group of atoms together

-a single bond has a bond order of 1, a double bond has a bond order of 2, and a triple bond has a bond order of 3.

-Fractional bond orders are also possible. If a molecule (ie. Benzene) can be drawn using two different structures, it exists as an average of those two structures

-covalent bonds form if heat is released when atoms bond

-a negative enthalpy of reaction means that the product is more stable than the reactants at constant pressure

**by convention, chemists typically write the reverse reaction equation and list the bond dissociation enthalpy (ie. how much heat is required to break the bond and move the atoms far enough away from each other that they don't interact)

-bond length is primarily determined by atomic radii. A bond between two larger atoms must be longer than one between two smaller atoms

-the length of the covalent bond between two atoms can be approximated as the sum of the covalent radii of the two atoms.

-generally, tripple bonds are shorter than doubles, which are shorter than singles. Longer bonds are weaker.

-the pure element or compound at a pressure of 1 bar an dat the temperature of interest

-standard enthalpy of reaction is the enthalpy change of a reaction in which all reactants and productts are in their standard states.

1) measure the enthalpy of the formation reaction directly

2)calculate indirectly using Hess's Law

-a process is a way to cause a change in a system

-defined by the beginning and end states of a system

-a reversible process is one during which the system is constantly in equilibrium with its surroundings

-isothermal: constant temperature during entire process

-adiabatic: no heat flow during entire process (open system, apart from heat)

-closed system: nothing tangible goes in or out

-isolated: no interaction with environment in any ways... more strict than closed.... reject EVERYTHING

-Clausius - second law

Kelvin - second law... dissipation of energy

-Clausius - concept of entropy

Entropy change can mathematically be defined as:

ΔS = q_reversable/T

-entropy means to give a direction

What is K_sp?