Chemistry key equations

Kinetic Energy

KE = ½mv²

Velocity

v = d/t.

Mass of an atom/isotope

mass number / Avogadro's constant.

Moles

Mass / Mr

Mass

Mr x Moles.

Molar Mass (Mr)

Mass / Moles.

Concentration

moles / volume in dm^3

cm^3 to dm^3

divide by 1000

moles

Moles equal Volume of gas (dm³) x 24

moles

number of particles / avogadros constant

Ideal Gas Law

pV = nRT ( pressure-Pa, volume-m^3, temperature-K )

dm^3 to m^3

divide by 1000

moles

number of particles / avogadros constant

celsius to Kelvin

K=C+273

Percentage Yield

Actual yield / theoretical yield x 100

Atom Economy

(Mr of desired product / Mr of all reactants) x 100

Density

Mass / volume, typically in g/cm³.

Energy Change (q)

q = mcΔT

Hess's Law

combustion data: enthalpy change of combustion = reactants - products

Formation data: enthalpy change of formation = products - reactants

enthalpy change

q / n

enthalpy change

bonds broken - bonds formed

standard enthalpy of formation

enthalpy of products - enthalpy of reactants

change in S

entropy of products - entropy of reactants

Gibbs free energy equation

ΔG = ΔH - TΔS

When change in G = 0 the reaction is feasible

ΔH - TΔS = 0

T = ΔH / ΔS

rate

rate = change in concentration / time

Arrhenius equation

K=Ae^(-Ea/RT) where A is Arrhenius constant, Ea is activation energy, R is gas constant, T is temperature in kelvin and e is exponential

Arrhenius equation

lnk=lnA-(Ea/RT)

mole fraction

gas moles of A / total mass of all gases

Partial pressure of gas A

mole fraction of A x whole pressure

EMF

EMF = E (reduction cell) - E (oxidation cell)

E (reduction cell)

usually on the left

E (oxidation cell)

usually on the right

Kw

Kw = [H+][OH-] (where Kw is the ionic product of water)

Ka

[H+][A-]/[HA] (where HA = weak acid )

pH

pH=-log10[H+]

at half equivalence pH =

pH = -pKa = -log10[H+]

Ka

10 ^-(PKa)

change in E

change in E=hv or change in E= hc/wavelength, where h is Planck's constant, v is frequency of light absorbed, wavelength in m, c is speed of light