Extra stuff to know Flashcards
Infrared radiation bonds/atoms
Absorb IR - makes them bend/stretch - heavier atoms vibrate more slowly
Stronger bonds vibrate faster
IR radiation atmosphere
Relatively unaffected by atmospheric gases - passes through atmosphere to earth’s surface where most is absorbed and some is re-emitted in the form of longer wavelength radiation ; greenhouse gases absorb THIS radiation and they re-emit as radiation which increases temp of atmosphere leading to global warming
Applications of IR
Many pollutants can be identified by their IR fingerprints
Breathalysers - more IR radiation absorbed from ethanol = more ethanol
UV
Ozone absorbs UV radiation from Sun’s rays on,y allowing a small amount to reach earth’s surface -
When measuring change in entropy
MOLES of gas matter
Reactions for fuel cells
Overall is the Enthalpy change that accompanies the formation of 1mol of H2O (l)
Acid fuel cell oxidation
H2 -> 2H+ + 2e-
Alkali fuel cell oxidation
H2 + 2OH- -> 2H2O + 2e-
Colour of copper iodide
White
Example of optical isomerism in transition
1-2 di amino ethane with 2 cl2 and Co central metal ion (+1 charge overall)
Cis platin
Pt central with 2cl and 2 nh3
Testing for bromine extra test
Use CONCENTRATED AMMONIA
Why do you use HNO3 first
Get ride of the possible white precipitate and any carbonate ions
Light brown precipitate
Mn(oh)2
Which hydrogen halide forms the strongest acid
HI - weakest bond Enthalpy thus dissociates to produce H+ ions when dissolves in water
Why are di carboxylic acids more soluble?
They contain 2 OH groups
When doing organic synthesis
Make sure to always add in HEAT
When asked to explain hydration Enthalpy
Always link it to attraction to water molecules
When asked to describe how anything except temperature affects K values (like Kc)
Just talk about how denominator and numerator changes to reverse the change and restore Kc
When talking about how Enthalpy change of solution changes
RATIO of energy produced to number of moles is the same
Why does Al have smaller ionisation energy than Mg
Mg has outer electron in 3s and Al has outer electron in 3p ; 3p is higher
Hexaaquacopper + KI
Copper iodide = white precipitate
I2 = brown solution
Cl2
Pale green
Bromine
Orange browney
Neutralisation
Exothermic
Why is water bath used
Easily controlled
And alcohol is flammable
Mno4 titration
Colourless to pink
Mno4- colour
Pink
Mn2+ colour
Colourless
Mno4- + Mn2+ ions
LOOK AT EQUATION AND HOW COLOUR CHANGES IN TITRATION
How to figure out degree of unsaturation via bromine molecules
Add in bromine dropwise - whichever one requires more drops = more unsaturated
If NH3 turns into NH4+ or a species forms a positive charge
LIKELY THEY HAVE ACTED AS A BASE - ACCEPTED A H+
When talking about H+ and OH- in half cell reactions
Equilibrium position what has reacted/been removed and then talk about E CELL VALUES
Enthalpy change (delta H)
Multiply by the number of moles (Stoichometry - number in front of species)
Explaining why delta G always positive/negative?
Break it down into what happens to delta H and t delta S
If increasing initial amount of a reactant in moles
The equilibrium amount of that reactant increases - shifts to the products and that increases too
BUT THE OTHER REACTANT DCEREASES - MORE OF IT HAS REACTED ; KC REMAINS THE SAME
When doing nitration of benzene
Concentrated HNO3 and CONCENTRATED H2SO4
Any aqueous (no solid) half cell
Include platinum electrode and like iodine aqueous and ions in solution
Zn + CuSO4
Blue to colourless - zinc displaces copper
When making standard solution
Add in LESS than 250cm^3 of water
When describing disproportionation
Use the word element not species
Redox reaction copper + iodine
2Cu2+ + 4I- -> 2CuI + I2
When explaining kp shifts
The last shift always = le chateliers
If you increase pressure of equilibrium
Increases pressure of the side of the equilibrium with the most amount of moles
Ratio of kp changes
THEN EQUILIBRIUM CHANGES WITH LE CHATELIERS ALWAYS THE FINAL SHIFT IS LE CHATELIERS
Mg + water
Magnesium hydroxide + hydrogen
Magnesium water
Magnesium + water -> Magnesium hydroxide + hydrogen
Pre exponential factor A
Is responsible for increased frequency of collisions + correct orientation
Graphite and graphene
3 bonding regions - 1 delocalised electron donated can conduct electricity
120 degrees - hexagonal layers
Limitation of average bond Enthalpy
In gaseous state
AVERAGE calculated form bonds in different chemical environments
Q=mcΔT
Dissipation of heat to surroundings
Incomplete combustion
Evaporation of methanol ALL LESS EXOTHERMIC
Non standard conditions
As rate increases
So does k
Mno4- to mn2+
Deep purple to colourless - read from top of meniscus
Electrons in half cells
If mixed together (the solutions) they will flow uncontrollably and release energy
Acid vs alkali fuel cell hydrogen
Continuously supplied with fuel and oxygen
No CO2 produced
Acid more negative electrode
H2 -> 2H+ + 2e-
Alkali more negative electrode
2OH- + H2 -> 2H2O + 2e-
Why is a excess of a species used in a rates question?
To keep the equilibrium far to the other side -look at EQUILIBRIUM POSITION
When talking about pH ratio
[HA]/[A-]
Reaction with double the Stoichometry?
To figure out Kp just square root the Kp of the reaction with double the species
At an equivalence point what is present?
Only salt and water
End point
Point in a titration where the indicator changes colour
What do we want with end point and equivalence point
We want both of them happening at the same time (as close together as possible) - end point should lie somewhere on that straight line (equivalence point is at the centre) - so we can observe sharp colour change
What is the colour of an indicator at end point
It’s in between the acid and alkali colours so should be in the middle
ph Probe
Remove from storage solution and rinse with distilled water
Ph probe storage solution
Buffer solution KCl
Phenolphthalein
Colourless in acid to red/purple in alkali
Bromothymol blue
Yellow in acid and blue in alkali
Methyl orange
Red in acid and yellow in alkali
Strong base weak acid
Phenolphthalein
Strong acid weak base
Methyl orange
Standard hydrogen half cell
Hydrochloric acid 1mol dm^-3
Hydrogen gas at 100kPa
Inert platinum electrode
Does salt bridge react with solution
NO
Non rechargeable cells
Provide energy until all chemicals have reacted
Rechargeable cells
Chemicals in the cell provide electrical energy - when recharging the reactions of the cells can be reversed
Rechargeable cell example
Lithium ion batteries
Drawbacks of lithium batteries
Toxic if ingested and rapid discharge of current can cause fire
Disadvantage of fuel cells
Hydrogen is flammable with low bp ; hard and dangerous to store and transport
Why might emf of a cell change over time
Concentration of ions change - reactants used up
To keep emf constant
Ensure that reactants are supplied continuously
[Cr(H2O]6]3+
Violet
Mn2+ aqua
Pale pink
Lime water + carbon dioxide
Forms calcium carbonate
Enthalpy change of solution
Lattice Enthalpy + hydration Enthalpy together - they BOTH have an effect
How to improve accuracy of titration
Take repeats
Reduce percentage error
3dp mass balance should be used
Condensation
Exothermic
What do photodegradable polymers break down into
Small particles of plastic that are biodegradable
Formation of amines?
NH3 + haloalkane makes salt first
Then react salt with NaOH to make the amine
TLC positioning
The plate is placed in a beaker of the solvent such that level of solvent is below the line
Inert carrier gas example
Helium or neon
Stationary phase of GLC
A liquid - solubility of sample in stationary phase is what determines it
Why use a minimum amount of hot solvent?
To get a saturated solution - if too much solvent added then solution may be too dilute to form crystals ; more likely to dissolve any impurities if you use a lot of solvent
Why to wet filter paper?
Keep it in place for the filtration
When reducing nitrobenzene
Form NH3+ initially with Sn and HCl then NEUTRALISE WITH NAOH and this forms NH2
Ch3COCl
Can polymerise without a catalyst
Whenever describing heterocyclic fission
Both electrons from the COVALENT BOND are transferred
Practical techniques organic
Dissolve in a minimum amount of hot solvent
Cool
Filter
Dry
Longer chain
MORE SURFACE POINTS OF CONTACT
Nucleophilic addition nitriles
NaCN + H2SO4
Nucleophilic substitution
KCN (in ethanol)
If it accepts a proton in a reaction
It is classed as a BASE
With further substitution (radical substitution)
Going to need 2Cl2
Will create 2HCl (this is a di-substituted product)
CFCs
Very stable - high bond enthalpies ; only attacked by UV in stratosphere
Phenol + bromine
Decolourise and WHITE PPT
C=C bond nature
LOCALISED
Area under curve for GC
Relative concentration - actual concentration = use a calibration curve
Primary/secondary/tertiary amines or amides
LOOK AT CARBON CHAINS ATTACHED TO NITROGEN
Why can a given Kc expression be used to calculate Kc
Because units cancel - same number of moles each side?
Why is Enthalpy change of solution the same?
Same energy released per mole of H2SO4
Why do we use a solution in excess
Concentration of HCOOH remains constant?
