chem 4

what kind of ploymer is non biodegrable

addi=tion

formal charge formula

valence electrons - (bonded electon/2 + non bondeded electron)

types pf chromatography

colomn

paper

thin layer- al plate with sio2 coating

chromatography

technique used to seperate components of a mixture base don their relatibe attraction invlving intermoleculat forces to mobile ans stationary points

components of chromatography

mobile phase

stationary phase mobi

mobile phse

solvent or gas that moves through the stationary phase caryiing sample components

stationary phase

solid or liquid medium through which the sample components are seperated based on their interactions

principples of seperaton

• movement of components in the mobile phase is controlled by the significance of their interactions with mobile/ stationary phse

• bc differences in factos such as solubility of certai components in the mobile phase and strength of affinities for the stationary phse - changes speed of components and hence seperation

  • these affinities involve IMF `

heat

form of energy which is transformed as a result of adifferrence in temperature annd produces an increase in disorder of the behaviour of the particles. inc in avg ke

enthalpy

• heat content of substance

• internal energy in reaction s

• abs vakue for enthalpy of reactants and products cannot be known but you can measure their difference

open

closed

iso system

open - mass and enegy change

closed - energy only

iso - no exchange

factoes o temperature

mass

amt of heat added

nature of substance

specific heat capicity

amt of energy needed to inc unit mass temp by 1k or 1c

exo and endo energy profile

is a reaction normally endo or exo

normally exo but if entropy is large it can be endo s

standrad enthalpy change = delta h 0

heat transderred at a constant preassure under standard conditions and states. can be determined from the change in temp of a pur substance

standard contopns not stp

t = 298k

p = 101.325 kPa

conc = 1mol/dm3

all substance in standard states ( pure substance_

c of water

4.18 J/kg

delta h formula energy

Q/n = energy/no of moles = J/mol

enthalpy of combustion delta h c

always negative

delta h c formula

enthalpy of combustion

consider situation ethanol is being used to ehat water

mc delta t/ n

m of water

c of water

delta t of water

n of ethanol

alcohol + excess o2 → co2 + h2o - delta h comvustion

reasons for diff in delta h experimental and lit

• heat lost to surroundng

• combustion may not be complete

  • ot underr std sonditions

delta h of reactions in solution

• carry out reaction in an isolated system such as polystyrebe cup or styrofoam

• heat released or absorbed by reaction can me measured byt he change in temp of wate r

• largest source of error is heat lost to env

delta h = -mc delta t/ n limiting

assumptions of delta h

soln is very dilute - vol of solute= vol of water/solvent

density of water = 1g/cm3

no heat loss from syet,

compensation for heatloss diagram

when it goes up thats whe reactant was added

if you extrapolate the decreasing gradient part of the curve back, at the time when reactant was added youll find the theoretical max temp vs t1 which is the actual max

delta t = t2 - t1

enthalpy of formation `

the energy change (absorbed or released) when one mole of a substance is formed from its constituent elements in their most stable, standard states under standard conditions

enthalpy of formation formula

sum of delta hf of products - sum of delta hf od reactants

delta hf for an element value

0

enthalpy of formation is for 1 mol

how to find hess law diagram

they will give main reaction eqn + 1 formation

add those 2 and cancel same stuff on opp sides

that is the bottom part of triangle + whatever else you need to satisfy all the formations

only multiply enthalpy by num of moles for combustion not formation

entropy unit

J/K mol

entropy

measure of distribution or dispersal of matter/energy in the system the more ways it can be distributed the higher the entropy. gas > liq > solid

spontanelosu reaction

spontaneous when it moved towards either completion or eq under a given set of contitions without external invervention. delta s is positve

non spontaneous reaction

reactions that dont take place under a given set of condiitons

factors of entropy

state = gas> liq> solid

no of particles - doubling particles doubles entropy

perfect ordered sold crystal entropy

0

entrppy and spontaneity relationship

delta s tot > 0 = spontaneous

delta s tot = 0 equilibrium

delta s tot < 0 non spontaneous

how to find temo where reaction becomes spontaneous/ non

delta g = 0 = delta h + Tdelta s

delta s 0 equation

sum of all n x s of products - sum of all n x s of reactants

n = no of oles

s = enthalpy

lattice enthalpy

enthalpy of a solid lattice - nacl→ na + cl2

borne haber cycle

delta hf + delta h lattice = delta h atomazitaion all + delta h ie all + delta h ea

ea = electron affinity

why would theoretical delta h and exp be diff

preence of ionic / covalent nature leaidng to higher delta h

binding triangle

are covantnt bonds lattice

no

cimbustion is redox

specific energy of a fuel formula

enenrgy/ mass

enthalpy formula energy and moles

energy/moles

rate of reaction

change in conc of a particular reactant/ product pre unit time

rvg rate of reaction formula

mod ( change in conc/ change in time)

how to find taye of reaction from graph

initial rate = tangent at initial

avg rate - final to initial line

instantaneous - tangent at point

collision theory

colliisons of particles must have suffieinent energ ymore than ea - energgt used to break binds in reactants - not individial particles energy but energy of the collison

and correct orientation - collision geometry - atoms come in direct contact and form chem bonds of products

why does reaction place even tho theres low % of sucessful collisions

high no of collisons/ second fa

factors affecting ror

preassure

conc

temp

surface area

catalyst

delta h 0

std enthalpy change

enthalpy of reaction

enthalpy change wen reactants in the stoicometric eqution give producsts under standard conditions

enthalpy of formation

when 1 mol of compound is formed from elements in std condition

enthalpy of combustion

when 1 mol of substance combusts

alw exo

enthalpy of neutralization

when 1 mol of water is formed by reacting an acid and alkalai under std condition a

avg bond energy

eergy needed to break 1 mol of monds in a gaseous molecule averaged over simmilar compounds

simplify eqn so only 1 mol is reacting

avg bind eneergy formula

total bond dissociation energy/ no of bonds

delta h 0 formula

ehthalpy change for bonds broken+ enthalpy change for bonds formed

for hess law eqns what sums equal what

clockwise = anticlockwuse

enthalpy of reaction formula

sum of delta h compubstion reactants - sum of delta h combustion products

born haber sycle endo and exo`

up is endo

down is exo

1st e affinity

std enthalpy change when 1 mol of gaseous atons is convetered to 1 mol of gaseous ions each w a -1 charge

endo exo or neutral

2nd e affinity

-1 to -2

endo

atomisation

splitting of cl2

atomization refers to the process of breaking down a substance (element or compound) into its individual constituent atoms in the gaseous phase. [1, 2]

delta h f eqn born haber cycle

delta h atomizatoin + delta h ie + delta h ea - delta h latice

reaction mechanism

series of elementaey steps by whcih a chemical reaction occurs. more than 1 step is a multistep reactioj

molecularity

number of species involved in an elementary step

uni molecular

bi molecular

termolecular

why is termolecular rare

3 particles r very unlikely to collide w eachother at the same time and in the correct orientation

rate determining step

slowest step

intermediate step

formed in 1st step and consumed in next step

rate proportiona to what `

conc of reactants

rate equarion

k[a][b] = rate

energy profile for multi step reaction

overall ea is the highest state - reactants stare

slow step is step w highest ea

what do rate eqns depend on

mechanism of the reaction and only can be determined experimentally

order of reaction

the exponent to which the conc of the reactant can describe the number of particles taking part in the rate determinig step

order w respect to reactant can desctibe the number of particles paking part in the rate determing step

overall reaction oderr

sum of orders w respect to reach reactant

rate law eqn

rate = k [A]^m[B}^n

m and n are experimentally found - mole ration

zero order rate and unit

rate = [A]

mol/dm³se

1st order rate and unit

rate = k[a]

mol/dm³s/mol/dm³= 1/s

2nd order rate and unit

mol/dm³s/(mol/dm³)² = dm³/mol s

3rd order unit

mol/dm³s/(mol/dm³)³ = dm^6/mol²s

zero order conc vs time and rate vs conc graph

first order conc vs time and rate vs conc graph

second order conc vs time and rate vs conc graph

hwo to find order from table

when a doubles and rate also doubles

order = multiplication factor of rate a/ multiplication factor of conc

what to do when both rates change

• you alr have oder of a from b4

• divide multiplier of rate by a order

  • then divide that value by 2 to get b value

when it asks to describe bodn what to talk abt

type pi or sigma

hybrdizatio

axial or lateral

why would structure not be accepted

formal charge why ou

why would molecule not have resonance structure

no way to draw lewis structue w fc equally close to 0

lp and bp try to minimisr replusion

why does more braching mean lower boiling point

smaller sa

weaker ldf needs less force to overcome

hybridization is from number of ed lp and bp

wh

what to sau when it says predict and explain bond angle

angle

no of ed e

electron mobility in graphene

nore bcs nor impeded by layers

how does sp2 inc melt

partial, stronger double bond character

arhenneus equation

uses temp dependance of the rate constant to determine activation energy

take sinto account frequency of collision s with proper orientations