Physical Chemistry Year 2

perfect gas equation

PV\=nRT

volume

size of occupied space

pressure

force divided by area to which the force is applied

temperature

property that indicates the direction of the flow of energy through a thermally conducting rigid wall

Boyle's Law

P x V \= constant

Charles' Law

V \= constant x T (at constant p)

Dalton's Law

at constant volume and temperature, the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of the component gases

partial pressure

the pressure that would be exerted by one of the gases in a mixture if it occupied the same volume on its own.

compression factor

Z \= Vm/Vm0

Thermodynamics

study of heat and temperature and their relation to energy and work

The Zeroth Law

if 2 systems are in equilibrium with a third system, they are all in equilibrium with each other

the First Law

energy is conserved in time. neither created nor destroyed

The Second Law

the total entropy (system + surroundings) never decreases

The Third Law

Entropy goes to 0 as T -\> 0
Entropy is disorder

system

a reaction vessel e.g., an engine or conical flask

surroundings

everything outside the system e.g., air, nitrogen

open system

matter (gases) and energy (heat) can be exchanged with the surroundings

isolated system

both matter (gases) and energy (heat) cannot be exchanged with the surroundings

closed system

matter (gases) cannot be exchanged but energy (heat) can be exchanged with the surroundings

diathermic

allows the free passage of heat over the boundary

adiabatic

does not transfer heat over the boundary

isothermal

A process in which temperature of a system is constant

spontaneous process

a real process that can take place in a finite time period. irreversible

reversible process

an imaginary process in which the system passes through a continuous sequence of equilibrium states

impossible process

a change that cannot occur under the existing conditions, even in a limiting sense

internal Energy

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

Potential Energy (PE)

stored energy

thermal energy

the heat put into or taken out of a system

heat

The energy transferred between objects that are at different temperatures

work

an amount of energy put in to change a system by organised motion

Work equation

W\=Fd
w \= mgh

thermal equilibrium

where the systems are at the same temperature

thermodynamic equilibrium

where there is no net change of macroscopic properties (matter or energy) between systems over time

Gibbs free energy

combination of entropy and enthalpy. if positive, reaction is nonspontaneous. if negative, reaction is spontaneous

standard free energy change equation

ΔG \= ΔH - TΔS

enthalpy

measure of the internal energy plus the sum of pressure and volume

standard enthalpy of formation

enthalpy change involved when 1 mole of substance is formed from elements in their standard states. ZERO

enthalpy change for a reaction

∆H \= ∆H(product) - ∆H(reactant)

entropy

measure of disorder + heat transfer effect. how much the energy of atoms and molecules becomes more spread out in a process

Born-Haber cycle

An enthalpy cycle that allows you to calculate the lattice enthalpy change of formation for system.

Hess' Law

If a reaction can take place by more than one route and the initial and final conditions are the same, the total enthalpy change is the same for each route.

a reaction becomes feasible when delta G is...

negative

standard entropy

the entropy of one mole of a substance at 1 atm and 298K

extensive property

value dependant on the amount of material e.g. mass, volume, energy, texture

intensive property

value independent on the amount of material e.g. density, temp, conc, viscocity

Internal energy equation

deltaU \=q + w

Adiabatic bomb calorimeter

measures internal energy. record temperature by Q \= C deltaT

calorimetry

study of heat transfer

flame calorimeter

used to find the enthalpy of combustion of a substance

transfer of heat and work into the system \=

positive

transfer of heat and work out of the system \=

negative

heat capacity

quantity of heat required to raise its temperature by 1 degree

heat capacity equation

deltaQ \= cm deltaT

molar heat capacity

heat capacity per mole of a substance

specific heat capacity

heat capacity per mass of a substance

heat capacity at constant volume

Cv \= (dU/dT)v

heat capacity at constant pressure

Cp \= (dH/dT)p

adiabatic changes of a perfect gas

w \= Cv deltaT

Enthalpy equation

H \= U + PV

Enthalpy of a perfect gas equation

deltaH \= deltaU + delta nRT

lowercase d

extremely small or partial

internal energy \=

kinetic energy + potential energy

change in internal energy

ΔU \= Ufinal - Uinitial

effect on internal energy with increasing temperature

positive

effect on internal energy with decreasing temperature

negative

Compressing a gas

causes molecules to move faster, increasing the internal energy. work done on the gas is positive

expanding a gas

causes molecules to slow down, decreasing the internal energy. work done on the gas is negative

Pascal (Pa)

SI unit of pressure; 1 Pa \= 1 N/m2

1 atm to Pa

1.013 x10^5 Pa

deriving work done method

1) work done equals the force x distance
2) pressure equals force/area (rearrange for F)
3) combine 1 and 2
4) the "Ad" is the same as the change in volume
5) combine 3 and 4 to get an expression for the work done

Isothermal reversible expansion of a perfect gas

w \= -nRT ln(Vf/Vi)

consequences of 2nd law general

in a system, a process that occurs will tend to increase the total entropy of the universe.

consequences of 2nd law: Lord Kelvin

it is impossible to convert heat completely into work in a cyclic process. you cant get a 100% efficient engine

consequences of 2nd law: Clausius

heat generally cannot flow spontaneously from a lower temp to a higher temp

consequences of 2nd law: carnot engine

theoretical engine that specifies limit on the maximum efficiency a heat engine can obtain

phase

a part of a system that is chemically and physically uniform throughout. Gas, liquid or solid

components

number of independent substances which must be specified so that the composition of each phase is described

degrees of freedom

number of intensive variables which can be independently varied without changing the number of phases

Gibbs Phase Rule

the number of intensive variables that must be defined to determine the state of the system.

F \= C - P + 2

Superfluid

A fluid that has zero viscosity which flows without any loss of kinetic energy. when stirred, it forms vortices that continue to rotate indefinitely

Vapour pressure

The pressure exerted by a vapour at equilibrium with its liquid in a closed system. indication of evaporation rate

phase diagram

a graph showing the conditions at which a substance exists as a solid, liquid, or vapor

phase boundary

shows the value of pressure and temperature at which 2 phases can co-exist. Steep slopes \= huge pressures needed for significant change

boiling

the condition of free vaporisation throughout the liquid

melting

the temperature at which under a specified pressure, liquid and solid phases co-exist. AKA the freezing temperature

Triple Point

the point at which all 3 phases co-exist in equilibrium

Critical Temperature

temperature at which the density of vapour and liquid are the same. Occurs when heating a pure liquid in a sealed container. The liquid doesn't exist.

Raoult's Law

the vapor pressure of a solution of a non-volatile solute is equal to the vapour pressure of the pure solvent at that temperature multiplied by its mole fraction

Raoult's Law Equation

P \=Xsolvent x Psolvent

calculating vapour pressure

1) work out no. of moles of each substance
2) work out total no. of moles
3) work out the mole fraction of both substances
4) apply and extend the formula

Electrochemistry

the investigation of reactions in solution in terms of chemical measurements

if solute ionises in the solvent then:

solution \= electrolyte

Ohm's Law

V\=IR

Potentiometry

measurement of potential difference (voltage)

Voltammetry

Measurement of electrical current

Conductivity

the measure of a solution's ability to conduct electricity. measurement of resistance / ohms

electrochemical cell consists of:

2 electrodes, an electrode compartment, an electrolyte, a power supply and/or a voltage measuring device

salt bridge

connects the oxidisation and reduction half-cells of a galvanic cell, a type of electrochemical cell

redox reaction

a chemical reaction in which there is a transfer of electrons from one species to another

reducing agent

electron donor