Last Second Things Forgotten

Question 1

Group 2 bases
Agriculture and medicine

Answer 1

Ca (Oh)2 is limewater and used to neutikise acidic pH soils

Mg(oH2) 2 milk of magnesia used to treat indigestion by neutrilsing excess acid, soluble enough to get there but not soluble enough to pass into system

Question 2

Iodine state at RTP

Trend of halogens going down

Answer 2

Is SOLID

Boiling increases due to more electrons thus more London etc

Question 3

Reactivity of halogens going down

Halogen displacment reactiosn

Colours

Answer 3

Decreases, need to attract an electron, nuckear attraction decreases lower you go hence reactivity decreases

A more reactive halogen will displace a less, releasing that into solution

= chlorine green green
Iodine is orange then orange
Iodine is BROWN THEN VIOLET in organic solvent

Question 4

How are acids from disportionation bleach show

Answer 4

Add indicator red then white

Question 5

Advantages disadvantages of chlorine use with water

Answer 5

Kills bacteria which makes water safe to drink

However chlorine could end up reacting with hydrocarbons tk form chlorinated which are CARBIN one if AND TOXIC CHLORINE GAS

But clean water clear

Question 6

Ammonia test

Answer 6

Ammonium ions to hydroxide ions, thr. Heat , damp paper, turns it red to blue

Ammonia used ti differniate silvers, where solubitliy decreases lower you go

Question 7

Standard conditions

Answer 7

Temo is 25! 100 KPa , 1 Molsm conc

Question 8

Enthlapy changes
Reaction

Formation

Combustjon

Neutiksiation

Answer 8

The enthlapy change that accompanies a reaction in its MOLAR quantities

Enthlapy change that accompanies the formation of ONE mole of product from constituent elements under standard etc

Enthlapy change that accompanies complete combustion of one mole of fuel under standard

Enthalpy change neutrilisation : the e enthlapy change that accompanies ONE MOLE OF water formation from acid and base etc, constant value around -57

Will have to divide / multiply moles accordingly

Question 9

3 reasons less Exothermic

Tips to reduce?

Calculations “

Answer 9

Evaporation from wick
Incomplete combustjon
Heat loss to surroundings
All means more moles so less value

Non standard could could not

= use draught screens to block wind, oxygen canisters to ensure complete

Ensure all mass of what’s being heated up is used, and moles of what is required ( water, fuel, product) depending on enthaloy used

Question 10

Average bond enthlapy

Limitations (2)

Answer 10

Energy required to break one mole of a specified type of bond in a gaseous molecule

1) average
2) defined at gaseous whereas most don’t take part at that

Question 11

Hess law formation

Answer 11

Remember enthlapy of formation for an element is 0, for everything else clockwise = anti-clockwise
Combustjon down, formation up , else manipulate until achieve equation you want

Question 12

Why is it hard to determine combustjon direclty?

Answer 12

• form so many other compounds that dozens of compounds formed impossible to measure , hence must be used indirectly Hess

Question 13

Collision theory

Answer 13

Concentration = means more collisions , temp 2 , sa means more reactsnt moelcules exposed ti be reacted at any time so more collisions etc

Need to collide with correvt orientation , ea and collide, so often hard for one step reactiosn as unlikely this can happen, hence multi step

Question 14

Effect of catalyst benefit disadvantage

Answer 14

Means companies need lower tempertaures and thus less energy, hence less fossil fuels burnt, hence less emissions and co2

HOWEVER some catalysts are toxic so must be considered, overall still better

Question 15

Boltzmann ea temp

Answer 15

Ea means higher proptinal has ea

Increase temp means more molecules has old ea

Question 16

Dynamic equilibrium

Answer 16

When rate of forward reavtion = rate of backward
Concentrations are the same
In a closed system

CALAYST increases rate of forward and backward but that’s it

Question 17

How else to recycle and used polymers waste

What’s the problem with recycling PVC

Answer 17

1) combustion for fuel
2) organic feedstock for other processed and chemicals

1) has cl such that di used for fuel can produce HCl which is TOXIC

Question 18

Why good biodegradable and how

Answer 18

Done as easilly hydrolysed by water

Means less waste, which is per meant normally, and also reducing dependency on finite resources

Question 19

Alchol reactions

Answer 19

Carboxylic , acyl chlorides all to form esters

NABr + h2so4 to produce halolakne, where reaction happens in vitu ( can use hcl instead )
Oxidations calm
Dehydration with conc acid caltyst to form teo alchols, where major product is on markownikoff rule again

Question 20

Rate of hydrolysis and test

Answer 20

Increases as carbon halogen bond decreases

Test with silver nitrate, aqeuous, and ethanol, which allows it to show
- hydrlysis occurs
- heat silver nitrate and separately ethanol and halolakne , and mix et

As STRENGHT kf bond decreases, easier to hydrolysed, greater rate

Question 21

How to do colorimeter

Answer 21

Identity what changing colour
- use OPPSITE colour wavelength filter, and zero with water
- take freuwney samples of known conc and measure absorbsncd whatever
- then plot curve and uses this to find the conc , can use to make a conc time graph to find rates and also potential order

Question 22

Iodine clock

Answer 22

Produces iodine from iodine ions which becomes orange but straight always uses by thisulfste which makes colourless

Once runs it blue black in presence of starch

Assuming less than 15% of reaction , the rare here is approximated to intial rates. This means with one calc you can get the INITAL rate , use it to plot rate conc graph, and find exact order

• thisulfste used to slow down else we never could see, too much could make too much of reaction so be careful

Question 23

Effect on temp , pressure on equilborum , kp / Ka explain

Answer 23

Temp= if forward Exothermic, then reduces ka , hence the top musr reduce, bottom increase so shift to left etc

I’d increase conc, the ka will be constant , but say increase conc product, now ka bigger, so to decreases back top decrease bottom increase shift to left

I’d increase pressure, increase pressure of reactsnt and product. Ka must stay the same, but because different molar ratios, it will be diff, thus to return back must chaneg such that goes to direction of smallest moles etc

Question 24

Why is 2nd disscoation weak acid

Answer 24

Bevause hard to remove a proton from an already negative intermediate hence partially disscoates, so ph is greater than expected

Question 25

Approximations for weak acid

Answer 25

Moles at equilborum of Ha would be Ha - H+ disscoates as one to one
- however weak acid, unlikely much , hence approximated to just Ha

Conc of H+ what be = to conc of Ha-, however h+ from disscoation if aqeuous wated.
- however if take this to be very small, negkible, hence h+ = A-, and thus H+

When break down?
- if Ka string enough then disscoation of h+ from acid noticeable hence first approximation breaks down
- if bery dilute or high TEMP, then Kw of water increases hence pH too, so this breaks down

Question 26

Kw

Answer 26

Increases with temp, is used to control all concs of Oh- and H+ at a certain temp

Remember Monobasic etc based too for strong alklai

Question 27

Hdyrogen cabrinste carbonic acid

Answer 27

Add acid, reacts with A-, producing more Ha thus equilborum shifts to left
Add alklai, reacts with h+ m reducing h+, so Ha dissocsted to increase, and shift to the right

ph human blood is 7.4, must be kept between 7.35 and 7.45, else enzymes denature

Question 28

How to measure pH. Urge

Answer 28

1) add some acid to a conical flask
2) usinf a pH probe, add the electrode to the flask
3) connect to a datalogger so it autmaotically measures
4) add thr base to the burette and SWIRL 1cm at a time
5) or use MAGENTIC swirled and add slowly
6) when approach the rapid pH change add very slowly
Then can plot graph

Question 29

Equivalnce end point etc

Answer 29

Equivalence when one volume matches other reaction fully, also middle of line
End point assumed to be same as equivalnce but when conc of Ha in indicator = A-, where the colour of the EQUILBKRUM lies in thr middle at that point

Indicators are just buffers really with different colours, and change of h+ or alklai causes it to be different colours, such that it goes through all as you go

The indicator chosen must fall in the range of the vertical section of graph

At end point as ha = a- PKa = ph again,

2) curves
Remember weak acid curve starts high and is curved due to acting like a buffer, finishes whatever, but because starts high the long part of graoh is high . Remember that 3 units vertical, and ,ost of it above pH 7

There is no indicator suitbsle for weak acid weak base at a
L

Question 30

Lattice enthlapy

Answer 30

Is the enthlapy change that accompanies the formation of one mole of ionic compound from gaseous ions

Question 31

Enthaloy change of soltution
Hydrstion

Answer 31

1) enthalpy change that accompanies one mol of SOLUTE dissolving in AQEOUS soltuion

2. Hydration is the ENTHALOY that accampiex one mole of GASOEUS ion dissolving in aqueous soltuon IN WATER

SOLUTION SEEMS to be the difference between energy released when forming bonds with water, against energy needed to dissociate lattice right, so if energy r,eased is more and soltuion negative dissolve? No, even with positve soltuion, due to entripy it could still be feasible

Base case ions GASOEUS at the top, note the soltuion could be positve or negative

Question 32

Effect of lattice enthlapy and hydration

Answer 32

Ionisc size increases, attraction ti water / ionic attraction decreases, so less energy released less Exothermic. Same with chwrge

If ENTHALOY chaneg less Exothermic lower melting point too , or greater

However other factors like bonding make a difference too

Question 33

Limitations of GIBBS

Answer 33

Only takes into account energies , not kinetics, such as ror , activation energy, such that just because feasible , might take 1000s years to complete

Question 34

Titrations

Answer 34

Colourless to permanet pink self indicating at end poitn

For iodine thisukfste what happens is a chemical in acidic environment is added to KI, where ioidne ions fully react to produce a SET AMOUNT OF IODINE, making it orange yellow.
When thsoldukfste in burette rescts, makes iodine iodine ions, so colourless
Hence colour fades
When approaches pale straw at starch tk accentuate the colour. Final change sk blue black to colourless
We add at the end because complex so string that reduces amount of iodine

Use balancing numbers ti find origami

Iodine ions to idoine , then whatever that is transfer to iodine in first equation and stoichmetry again

Remember go from left bala ne, then take to right and balance , scale etc

Question 35

Electrode cells

Answer 35

Most positve is positve electrode negative negative,

Most reductucing sn gent mkstcnnegativneetc
As metfsks lose electrons they become oizidised, so most reactive is negative agsin

Standard is measured against hydrogen h+ system at standard conditions , remember must be 1 mol and if it’s non metal then SAME conc not necasially 1 mol
Salt bridge allows ions to flow
E cell is positve - negstvif

Question 36

Limitations re,e,esr

Answer 36

1) conc not the same
- then based on the EQUILIBIRUM more or less electrons produced, hence more then the half cell ptoentisl becomes more mega y or / positve accordingly

2) DOESMT TAKE INTO ACCOUNT KINETICS AGAIN, no ror, ea
3) other condtions not standard will chnage the potentials meaning using these to predict womt be fully accurate

Question 37

Fuel and storage cells

Answer 37

Primary class non RECHARGABLE used once, two half cells,

Secondary cells RECHARGABLE, chemical process can be reversed to produce energy
Remember good for small, lithium blew up before
Fuel cells use energy made from fuel and oxygen to CREATE A VOLTAGE
- fuel and oxygen enter, produced leave
- electrolyte stays in the middle
- as long as continously powered keep going etc
# use fuel cell that doesn’t produce any emissions like hydrogen

Question 38

Acid and alkali fuel cells

Answer 38

Have h+ in both and oh. In both equations but give the same e cell

Question 39

Ligands

Answer 39

Remember sqaure planar only formed with platinum gold palladium else all tetrahedral

• cis platin used ti treat tumours by binding ti dna , causing apoptosis, however side effect is kidney damage, but is used

Cos trans can be shown by tetrahedral octahedral together oppsitr

But optical only by octahedral and must be 2 alone
The cis is optical and trans therefore 3 isomers

Cis trans shown in SQAURE PLANAR ROO!, where cis platin is two ammonia two chlorine
- remember these remove chadg

Question 40

Colours etc

Answer 40

In ammonia, cu Oh dissolves to form copper 4 ammonia 2 water
AND cr( Oh)3 dissolves to form cr (Nh3)6 (purple)

In excess Oh
Cr(oh)3 dissolves to form cr (oh)6 dark green

Colours forgot
Mn2+ pale pink to mn(oH2) light brown
Cr3+ is village becomes grey green then dark green

Cr (6 H2O) village ti purple

Remembe reactions with ammonia give the same, just represent with oh , etc

Question 41

Hamelglobin

Answer 41

Fe2+ central metal ion, form dative binds with fe2+ oxygen, when needed ligand sun with co2

However co forms strongest dative bonds, which irrevsieble so useles hamelglonin and thus toxic

Question 42

Extra colours

Answer 42

Cr2+ is blue, cr3+ is green 6+ / cr2o72- is orange obv

White cuI , brown I2, brown cu, fe 3+ to fe 2+ orange brown to green

Remember ti become fe 3+ need to become oxidised so someth else reduced

Cuso4 is blue, cu I’d brown, copper csn cisproptinate herr

Question 43

All NUCLEOPHILIC electrophikic reactiosn

Answer 43

E,ectiphikic additon is hbr to alkene , susbtition is nitration / brominstion / acylation etc of benzene / ohenol

Nuelcophilc substiopj is like Oh- with halolaken
Addition is H- or CN- with nabh4 H2O NACN h2so4 accordingly to alchol ketone reduction

Question 44

Overall reactions

Answer 44

Remember 2 o for reflux, one otherwise and ketone, one h2o released each time
2 h reduction, else hcn

Question 45

Organic reactiosn

Answer 45

Esterificsrion = cabroxykic acid alchol, acyl chloride alchol. Acid anhydride alchol ( and produces a cabroylic by itself), also like in amino acids whatever, sukfruic acid catalyst and reflux forms ester bond

Amides formed when acyl chlroide react with ammonia , and primary amines ti form secondary amides

Acid and base hydrolysis, acid hydrolysis returns the cabeknsylic acid fully and the alchol , but if amide then protonated
ALAKLI hydrolysis returns the carboxylate salt and alchol this time

Aycl chlroide reactive enough ti form esters with phenols, alchols, water cabroylic, whole point of being a derritiave is that if hydrolysed you form larent chain, thr ammonia and amine the amides

How to name amides? Longest chain but an amide, everything else N substituted in ALOHABETICAL ORDER ( can only be max 2 anyways)

Acid anhydrides less reactive so used instead of acyl chlrides, can form all phenol alchol amine ammnoia to make amides too

Question 46

Naming amines

Answer 46

If primary then burly amine, if last postiom
Else if Randi postion, 2 amino
If secondary teriwty then same as amide , main chain amine , N substituted

Question 47

Amine reactions

How to make

Aromatic ?

Answer 47

Act as bases as they have lone pair that can donate to a h+ to form a dative covalent bond, accept a proton hence a base
- react with acids fully absorb acid , become protonated

Halolakne + ethanol + excess ammonia then NaOH ( where excess ammonia presents sub again, ethnaol prevents hydrolysis of halolakne). Secondary means use primary amine instead of ammonia etc

Nitro benznen + 6 H and tin conc hcl and NaOH becomes phenyl amine , get rid of two o so 2h2o

Question 48

amino acid reactions

Answer 48

Amin and carbox group
- with acids protonated and soaked up
- with base, forms salt

With ESTER BECOMES PROOATED due to acidic conditions

Question 49

Amides esters condensation etc

Answer 49

Normal monomer means n-1 H2O formed
2 monomers is 2n-1 H2O formed
2 monomers when dill dicabrox, amino acids etc is only one

Acid hydrolysis of an amide protonated amine part, returns cabrox
Base hydrolysis returns amine, salt with acid , gives n back

Question 50

Nitrile

Answer 50

Formation = CN with ketones alchols hydroxyl nitriles
Or CN KCN and ethanol with halolakne gives

Now reduction of nitriles , 2h2 and ni caltyst 423k , forms AMINE

Hydrolysis, 2h2o + hcl forms cabroylic aicd and ammonium chloride

Other csbrin extenders are acylstiom , alkylation

Acylstiom makes a KETONE BTW with double o on first cabron

Question 51

Practical techniques

Answer 51

Büchner, remember to filter paper, let it reduce etc

Melting point, looking for sharp melting range, do trial, then low heat and accurately Det sin rnahe, more sharp the better more prue against a book

Solids impure lower melting but when boilign higher

Question 52

Chromatrgiphy

Answer 52

Stationary phase silica mobile solvent,

Gas = inert gas mobile, liquid adsorbed on inert solid

The degree of interaction between mobile vs stationary determines how far / how long it stays in chromatrgom, where retention times are used to compare
- pwak area represents concentration, so I’d run test with known concs can make a calibration curve to also determine its concentration

Remembe fecl3 to ohenol makes purple, else low ph as test

Question 53

Nmr

Answer 53

Run against nucleons and spin prop try which is apparent when odd
Hence done on carbon nmr and proton nmr, csbrkn13 isoptope @% present in all compounds, so useful

Deuterium even, so doesn’t show up, hence D2O etc is used for proton exchange to identity cabroxykic or nH groups , as they won’t appear. Cdlcl3 deuetared shows in cabron but filtered, good solvent, TMS has one group esch so used a st standard small peak on
Number of peaks represent number of environments

Remember splitting from non equivalent only, n+1
9 refers to certain types