formulas Flashcards
Relationship between frequency and wavelength
v=c/ƛ
where v=frequency (Hz) c=speed of light (3x10^8ms^-1) and ƛ=wavelength (nm)
Relationship between frequency and energy
E=hv
where E=energy (J) h=Planck’s constant (6.626x10^-34 Js) v=frequency
Factor of a metre: femto (f)
10^-15
Factor of a metre: pico (p)
10^-12
Factor of a metre: nano (n)
10^-9
Factor of a metre: micro (µ)
10^-6
Factor of a metre: milli (m)
10^-3
Factor of a metre: centi (c)
10^-2
Factor of a metre: deci (d)
10^-1
Factor of a metre: kilo (k)
10^3
Factor of a metre: mega (M)
10^6
Factor of a metre: giga (G)
10^9
Factor of a metre: Ångstrom (Å)
10^-10
Beer-Lambert Law
A=Ɛcl
where A=absorbance Ɛ=molar absorption coefficient at given l (M^-1cm^-1) c=concentration (M) l=distance light passes through sample (cm)
Bronsted-Lowry theory
For every acid there is a conjugate base
pH in terms of [H+]
pH=-log10[H+]
acidic solutions: [H+] > 1x10^-7M pH < 1x10^-7M pH >7
neutral solutions: [H+] = 1x10^-7M pH =7
equilibrium constant expression for aA + bB = cC + dD
Ka = ([C]^c[D]^d)/([A]^a[B]^b)
If K >1 product favoured
If K <1 reactant favoured
pKa in terms of Ka
pKa = -log10Ka
Henderson-Hasselbach equation
pH = pKa + log10[base]/[acid]
Le Chatelier’s principle
If a reaction mixture at equilibrium is disturbed, reaction occurs in the direction that opposes the change
First order rate law for aA + bB = cC + dD
v=k[A]^x[B]^y
First order concentration-time equation
ln[A]t=ln[A]o-kt
Second order rate law for aA + bB = cC + dD
v=k[A]^2
Second order concentration-time equation
1/[A]t = kt+ 1/[A]o
First order half life equation
ln2 = kt1/2
Second order half life equation
t1/2 = 1/(k[A]o)
Arrhenius equation
lnk = lnA - Ea/RT
where A=prefactor Ea=activation energy R=gas constant (8.314Jmol^-1K^-1) T=temp in Kelvin
Gibbs free energy
ΔG = ΔH - TΔS if ΔG > 0 spontaneous if ΔG < 0 non-spontaneous if ΔG = 0 equilibrium G = gibbs free energy (energy available to do work) H= enthalpy (the conversion of potential energy to heat) T = temp in Kelvin S = entropy (molecular disorder)
free energy and chemical equilibria
ΔG = -RTlnK
if K > 1 spontaneous
if K < 1 non-sponataneous
if K = 1 equilibrium
Boltzmann equation
S = Kb lnW
where S is entropy, Kb is Boltzmann’s constant (1.38x10^-23K^-1) W is the number of ways a state can be acheived
First law of thermodynamics
Energy can neither be created nor destroyed but merely converted from one form to another
Second law of thermodynamics
In any spontaneous process the entropy of a system and its surroundings always increases
third law of thermodynamics
The entropy of a perfect crystal at absolute zero is zero
Cell potential
ΔG = -nFE
where n is number of moles of electrons
F is Faraday constant (96485C/mol)
E = cell potential (V)
Nernst equation
E = E°cell - (RT/nF)lnQ
Q is the reaction quotient
