chemical reactions

what is the 1st law of thermodynamics?

energy cant be created

what is Hess’ law?

enthalpy of a reaction is equal to sum of enthalpies of reactions into which it may be divided, enthalpy is independent of route taken

what is the 2nd law of thermodynamics?

not possible to convert heat into mechanical work completely

what is the equation with: dH, dQ, dW, since its to energy-which part is the heat part, work part

dH= dQ (heat) + dW (work)

how can energy content be exchanged?

via heat or work

what is the equation that connects p, V, n, R, T

since its to do w energy- what is the work part and heat part

pV (work part)= nRT (heat part)

how can energy be described?

pressure, temperature, volume, amount (n)

what is the equation for gibbs free energy?

dG= dH-TdS

even if dG<1, activation energy is still needed, what controls the reaction if:

E_A is provided at norm level,

E_A is not provided at norm levell

if E_A provided at norm level- thermodynamic control

if E_A not provided at norm level- kinetic control

what is the Arrhenious equation?

k= Z x e^{-E_A /RT}

Z=orientation influence

e=reflects E_A influence (E_A /RT smaller= k is bigger)

what controls the reaction if k<1 or k>1

if k>1= thermodynamic control

if k<1= kinetic control

how does order of reaction correlate to rate?

rate= k[ ]^order

what is a Bronsted-Lowry acid and base?

acid- proton donor, base- proton acceptor

what is mass action law?

in a reversible reaction- the products and reactants have a ratio - represented by k

k= [C] [D]/ [A] [B]

what is the equation for speed of the forward reaction?

v_for = K_for [A] [B]

what is le Chatelier principle?

when a stress is imposed on an equilibrium the reaction will shift to relieve the stress

what equation connects log[H⁺ ] and log[OH]

-log[H⁺] - log[OH]= 14

pH + pOH =14

what equation correlates K_a and K_b and K_w

K_a K_b =K_w

what does a big K_a mean?

strong acid

what is an ampholyte?

weak acid +weak base

what is the Henderson Hasselbach equation?

pH= pK_a + log [A^- ]/ [HA]

how do you decide what half equation runs first? (when calculating dE)

more negative E runs first (electron flow goes from most negative cell to least) (dE)

what are the 2 types of electrode?

-metal rod in metal ion

-Hg, Hg₂ Cl_2, KCl paste, KCl solution, Pt wire (inert)

what are the limitation of pH electrodes?

if pH<1 as [H⁺ ] does not equal a_H

if pH>12 as [Na] interferes

light is polarised, allowing for interactions between light waves: what are constructive, destructive and intermediate interference

constructive- additive (crests and troughs align)

destructive-cancel out (crests align with troughs)

intermediate-no effect (crests or each wave 90degrees apart)

what equation shows the quantum mechanics of energy (of a photon?)

E=hv (h=planck’s constant)

(v=frequency) (e=energy)

what are the 3 ways of energy transfer?

translation, rotation, oscillation

what is the equation connecting translation energy, rotation energy, vibration energy, electronic excitation of energy?

total E= E_trans +E_rot +E_vib +E_elec

what is the order of the sizes of energies? (trans, rot, vib, elec) and what uses each kind of energy transfer?

dE_trans<dE_rot (microwaves)<dE_vib (infra-red)<dE_elec (Uv visible)

what is the equation for absorbed and transmitted radiation

absorbed= -log i/ i₀ (i= transmitted radiation, i₀=incident radiation)

transmitted= i/i₀

what is the beer’s law equation?

A= 3 x c x d

A= absorbance in given wavelength

3=molar absorptivity L/mol.cm

c=conc. mol/L

d=path length cm

what is the difference between π and π*?

π* is higher energy (π absorbs energy→ π*)

HOMO=highest occupied molecular orbital

LUMO=lowest unoccupied molecular orbital)

what do HOMO and LUMO arrangements look like?

what is Max absorbance characterized by?

3_Max and y_max (absorbance Max and wavelength Max)

what is the Nernst equation

how do double bonds affect 3_Max and y_max?

multiple double bonds- shift in 3_max ONLY

how does co-planar molecules & conjugated double bonds affect 3_max & y_max?

increases both

how is colour vision facilitated?

double bond systems

what is a bathochromic shift, hypsochromic shift?

bathochromic- red shift towards a longer wavelength, hypsochromic-blue shift toward a shorter wavelength

what is a hyperchromic, hypochromic shift?

hyper-intensity of absorption 3_Max increases, hypo- the opposite

what is the order of autochromes increasing wavelength (and generally decreasing in absorption intensity)

NR2 > -NHR > -NH2 > -OH > - Halogen > -OCH3

what are the two methods of ionising a molecule?

electron impact,

chemical ionisation (uses reagent gas ions) (has less fragmentation)

electrospray ionisation (uses strong electric fields)

Matrix-assisted laser desorption ionisation- (uses laser beam)

how are energy of acceleration and kinetics connected?