F334 Models Flashcards
1
Q
Enaniomers
A
Enantiomers are isomers whose structures are non superimposable mirror images.
2
Q
Phenol test
A
Neutral iron (III) chloride Turns from yellow to purple
3
Q
Addition of sodium carbonate to carboxylic acid (but not phenol)
A
Fizzing
Produces CO2
4
Q
Why is it important to have atom economy?
A
To reduce waste products
To ensure costs are kept to a minimum/ less energy is used
5
Q
Colorimetry
A
Make up standard solutions of known concentrations
Choose a suitable filter - complementary colour
Zero colorimeter with water
Measure absorbance of standard solutions
Plot calibration curve
Measure unknown solutions
Read off concentration from calibration curve
6
Q
Why can x act as a base?
-NH2
A
LONE PAIR on N/amine group
Accepts a proton
7
Q
Cis and trans isomers
A
There are two different groups on each Carbon of a C=C
These groups CANNOT rotate about the double bond
8
Q
Less trans isomers
Effect of crystallinity
A
Less trans linkages will make the chains less linked so they cannot line up and the crystallinity will be reduced
9
Q
DNA polymerisation reaction type and other product (with Sugar-phosphate)
A
condensation and water
10
Q
H bonding between bases
A
parallel dashed lines from the delta positive hydrogen to the lone pair on the nitrogen with a delta negative charge - interaction at 180’. Two bonds between thymine and adenine. (Three between cytosine and guanine).
11
Q
Successful outcomes of clinical trials
A
No harmful side effects: non-toxic
It works better than standard medicines.
12
Q
DNA finger prints of the innocent
A
Infringement of personal liberty
Fingerprint not unique; only probability
Techniques used not foolproof
Law might change accessibility
Helps to solve many crimes
Innocent until proven guilty
Future research into disease
13
Q
Condensation
Polyamide vs polyalkene
Water Absorption
A
-CONH, -NH, amide group allows nylon (a polyamide) to form H bonds with water molecules
No H bonding in neoprene (a polyalkene), so water molecules will force chains further apart
Chain less crystalline
Decrease in imb strength
Therefore Tg lowered
14
Q
Solvent properties for recrystallisation
A
The solvent should dissolve solute at high temperatures
The solvent should dissolve almost no solute at room/lower temperature
15
Q
Two stereoisomers would be expected to have different activities in the body
A
They have different shapes The active site has a specific shape One will bind with the active site better than the other Only one will form ESC They form ESC with different enzymes
Active site = reception
16
Q
Why does phenol reaction with NaOH and suggest why product is soluble in water?
A
Has phenol/phenolic hydroxyl groups
These groups are acids and neutralised by NaOH/OH-
Ions form
Ions are soluble
17
Q
Iron (III) and sodium hydroxide ionic equation
A
Fe3+(aq) + 3OH(aq)- —> Fe(OH)3 (s)
18
Q
mass spectrum
Species lost
17 m/z value of species lost
What is this species?
A
17 = 16 + 1
OH
A SPECIES LOST MUST HAVE NO CHARGE
19
Q
Species which form peak on mass spectrum have what charge?
A
+
20
Q
C14H12O3 + 3 OH- —>
A
C14H12O3 +3OH- —>C14H9(O-)3 +3H2O
21
Q
Mass peak at 93
A
C6H5O+
22
Q
Sodium carbonate
A
Na2CO3
23
Q
One mole of alcohol was reacted with one mole of ethanol chloride —>new functional group
A
Ester
24
Q
Element oxidation state
A
0
25
Reducing agent
| Allows reduction, gaining electrons
Loses electrons
Oxidation number increases
More positive
26
Following a reaction which produces iodine, I2, as well as uses up H+
Colour/absorbance
Iodine
By colorimetry
Concentration
Iodine
By titration
Acidity/pH
H+
By pH meter/titration
27
The rates of reaction were measured when the amount of reactants used up were small in comparison to the total quantities of reactants present
As reactants are used up
The rate will change - decrease
If relatively small amounts of reactants are used up, Concentration will remain almost constant
If relatively smaller amounts of reactants are used up, the rate measured will be for the initial concentrations
28
C2H3CONH2 + H2O + H+ --->
| Acid hydrolysis
C2H3CONH2 + H2O + H+ ---> C2H3COOH + NH4+
29
C2H3CONH2 + OH- --->
| Alkali hydrolysis
C2H3CONH2 + OH- ---> C2H3COO- + NH3
30
NH2 group
| Can behave as a base
Can accept H+
| Has a lone pair of electrons
31
AmiDe group
CONH2
| NotNH2
32
An Amide -NH3 : base?
Does not act as a base
| Does not gain proton
33
Unsaturated side groups
| React together to form cross links
Addition
| C=C bonds on side chains of different polymer chains open up and form a covalent bond
34
Carboxylation reagent
| -COOH to -COO-
NaOH
35
[Fe(H2O)6]3+
Shape
Coordination number
Colour
Octahedral
6
Yellow
Not green because for II (ee)
36
Diol and dioic acid
| Reaction type
Condensation
37
Cross links prevent dissolving
Cross links will prevent chains moving apart
Without cross links, water will force polymer chains apart and so polymer will dissolve
Water will form H bonds with chains COOH or OH groups
38
Addition vs. Condensation (or elimination) (to form co-product)
Addition has no atoms/products are wasted
Only one product
Therefore higher atom economy
39
Condensation with carboxylic acid: loses OH or H?
OH
40
Water absorbed by polymer
| What happens to concentration of dye in solution
The concentration of blue dye increased as water was absorbed
41
Suggest why it is easier to recycle the super-absorbent polymers from used nappies than the polymers from a mixture of used packaging
Used packaging consists of many different polymers which need to be sorted first
Lots of other compounds/additives in plastics used for packaging to be removed
Can wash/separate polymer from nappies and then heat to remove absorbed water
42
Why can a Voltage measured be different from standard?
The measured voltage is not done are standard conditions
43
Describe how the student used a colorimeter to find out how the concentration of the blue dye changed when added to the polymer
Select orange filter - complementary colour
Make up dye solutions of different known, standard concentrations
Measure the absorbance of the dye solutions of different known concentrations
Plot calibration graph of absorbance of readings
Add the polymer of known mass to the dye solution and measure the new absorbance
Take measurements until no further change in absorbance over a period of time
Use the calibration curve to find out how the concentration of the blue dye changes to find the concentration of the blue dye at different times
44
K2FeO4
| 'Green' oxidising agent
It is green (eco) because it forms iron III oxide (rust)product which is non polluting/ non toxic
Therefore often they can be out in landfill sites
45
Compound with 'sour taste'
Vinegar
| Ethanoic acid
46
Ethanol to ethanoic acid
| Reagents and conditions
Acidified dichromate
| Heat under reflux
47
Base
Proton acceptor
48
Phenol + carbonate
NO REACTION
49
No E/Z
C=C
Ring structure
Restricted rotation around the C=C bond
Each C atom in C=C has two different groups attached to it
The two -OH groups can only be on the same side of the C=C because the ring structure will not allow to rotate on opposite sides
50
Moldm-3 to gdm-3
Moldm-3 x gmol-1 = gdm-3
51
Ester hydrolysis
| Reagent
Concentrated HCl
52
Esterification
Coproduct
COOH
OH
H2O
53
Ether (vs. Ester )
No C=O
| R-O-R
54
Heating under reflux
The condenser is vertical
Mixture is evaporated, condensed, and returned to mixture
No substance is lost from the mixture
55
In distillation
The condenser is sloped downwards/horizontal
Mixture is evaporated, condensed, and collected
Mixture is separated
56
An increase in water absorption
More H bonding
| -NH, C=O vs. -O-
57
Decrease melting point
Weaker imb
| Less energy to separate chains
58
Increase in rigidity
Decrease in sliding of chains
Increase in aligned chains
Increase crystalisation
59
flexibility additive
Plasticiser
60
Zwitterions have a high melting point
They attract each other very strongly
Form a giant lattice
Ionic bonding is very strong
High heat energy required to separate particles
61
Thalidomide
| Used as a sedative in place of drugs at the time
```
More effective
Cheaper
Smaller dose required
Fewer side-effects
Can treat other symptoms
```
62
Testing of drugs of today to prevent thalidomide tragedy
Safety tests on drugs for use during pregnancy
Test to see if drug can pass through placenta
Longer period of testing
Longer clinical trials
Testing on pregnant animals
63
BrO3- +5Br- + 6H+ ---> 3Br2 + 3H20
| Why follow with Colorimetry
Reactants colourless
Br2 is brown
Change and increase in colour
Change and increase in absorbance in a colorimeter in the reaction
64
control variable
| Measuring Reaction rate
Temperature
65
Rds, slow step
Rate = k [BrO3-][Br-][H+]^2
Rds, slow step
Depends upon the species given in the rate equation
In this case, two H+ , 1 of the other species
2H+ and BrO3-
Forms
H2BrO3 intermediate
66
Some transition metal ions in solutions are coloured
Ions absorb specific wavelengths, colours of visible light
| Ions transmit complementary colour (wavelengths)
67
[V(H2O)6]2+
Coordination number 6
Shape of octahedral
Water
Dative covalent bond
68
d-block ions lose electrons from
4s first, before 3d
69
[V(H2O)6]2+
Can react with ammonia to form a new complex ion
Reaction type
Ligand substitution
70
Vanadium compounds can act as homogeneous catalysts because vanadium can exist in several oxidation states
True
71
In heterogeneous catalysis, vanadium can only use s electrons to form weak bonds on the catalyst surface
False
| 3d and 4s
72
Homogeneous catalysts provide a route of lower activation energy for the reaction
True
| For any type of catalysis
73
Forming polyamide
- COOH
- NH2
Condensation
| Water is eliminated, formed, lost
74
Crystalline polymers
Polymer chains are highly ordered/aligned
75
PPA has more crystalline areas
| Gives greater Tm
PPA chains are closer together
So imb in PPA will be stronger, more H bonds, more imb
More energy
Will be required to break imb
And melt polymer and allow chains to move over each other
76
Process to make a polymer more crystalline
Cold drawing
77
What is the opposite of addition?
Elimination
78
Carboxylic acid
| imb
H bonding
| id-id (as does everything)
79
Ester
| COOR
pd-pd
| id-id (as does everything)
80
DNA Monomer units
Nucleotide
| Formed from a pentose(deoxyribose + phosphate + a base)
81
The monomer units in proteins
Amino acids
82
Suggest why scientists once thought that proteins were more likely to transmit genetic data.
Proteins have more amino acids than the bases in DNA from which to construct many combinations to carry genetic data.
83
Ammonium peroxodisufate
(NH4+)2(S2O82-)
84
More positive E^-o-
The stronger oxidising agent
| Indicates a greater tendency to attract/accept electrons
85
State the measurements that would be recorded and indicate how these can be converted into concentrations of iodine
Take absorbance readings of the reacting mixture at known times
Convert absorbance readings to iodine concentrations using the calibration curve
86
Homogeneous catalysis
Reactants and catalysing are in the same phase
87
High resolution mass spectrometry
The masses of the different types of atom present are not integers/masses are measured relative to Carbon-12. Therefore Mass Spectrometry gives accurate four decimal place.
Comparison to Mr from database.pdifferent compounds with the same whole number molecular mass will have different Mr values from high resolution spectra.
88
MS peak at 15
12+3
CH3+
Must be positive to cause a peak
89
Charge on species lost from molecular ion
No charge
90
Adding Ethanoate group
Conditions
Reagents
(Esterification)
Heat under reflux
Concentrated HCl
Ethanoic acid
91
Recrystallisation
| Removes both soluble and insoluble impurities
Heat the impure sample with solvent with a minimum amount of solvent
(While hot,)Filter to remove insoluble impurities.
Leave filtrate to cool and crystallise
(After crystalisation, ) soluble impurities stay in solution
Filter off crystals, wash with cold solvent and dry.
92
Clinical trials - questions answered
1- Is it safe to be used in humans?
2- Is it effective?
3-Is it better than the standard treatment : an improvement on other drugs?
93
Adding bromine to two double bonds
| C24H31NO + 2 Br2 -->
C24H31NOBr4
94
Fe (II) + 2CH3COOH
Fe(CH2COO)2 + H2
95
Fe atom
4s2 3d6
96
Fe (II)
3d6
Lost the 4s2 e-
97
Fe (III)
3d5
98
Why are Fe (III) ions more stable than Fe (II)?
Half filled d orbitals (so less e pair repulsion)
3d5 not 3d6
99
Cerium (IV) sulfate
Ce (SO4)2
100
Green iron ppt left to stand
| Becomes red-brown
Red brown ppt iron III hydroxide, hydrated iron III oxide
Fe II ions/ Fe(OH)2 are oxidised (lose electrons) by oxygen.
Fe2+ --> Fe3+ + e-
Fe(OH)2 + O2 --> Fe2O3
101
Moles in 25cm3 to moles in 1000cm3
Moles in 25/25 x 1000
102
Compound A (carboxylic acid) is Insoluble in water but soluble in alkaline solution
COOH --> COO-
COOH functional group
Reacts with alkali to form ion is solution: soluble carboxylate
Carboxylate (COO-) forms bonds with water
103
IR 3150
O-H carboxylic acid
104
IR 1715
Ketone AND OR Carboxylic acid
105
Colorimeter
Calibration curve used to determine concentration of compound B as purple colour faded (to yellow) in titration flask
Show first order with respect to compound B
Use a filter that has complementary colour (yellow)
Put a sample of the reaction mixture into the colorimeter and take absorbance readings at set, regular intervals
Convert absorbance readings to concentrations using the calibration curve
Plot graph of concentration v time or 1/time for reaction
Determine half life from graph on the concentration v time plot
Constant half-life = first order
106
Peptide link in collagen
CONH
107
Amino acid zwitterion
NH to NH+
NH2 to NH3+
COOH to COO-
108
Enzyme activity less
| At temp Higher than optimum
Intramolecular/ H bonds break and active site is lost
109
Enzyme activity is less when pH is changes slightly from its optimum
Change in pH affects charges in active site
Ionisable groups are altered
therefore prevents correct interactions between enzyme and substrate
110
First order
| Substrate and enzyme
Rate = k x [substrate] x [enz]
111
Explain why at low concentration is substrate, the reaction is first order with respect to substrate.
Not all enzymes activities are filled/saturated
Substrate can form a substrate-enzyme complex
Active sites are available for substrates, which can bind to active sites
As the conc of substrate increases in proportion so first order
112
Give the new order of substrate and explain how it arises
All active sites are saturated
Ant increase in concentration of substrate will not affect the reaction rate
So order becomes or is zero.
[s]1 -->[s]0
113
Enzymes increase industrial process efficiency
```
Speeds up reaction rate
Reduces number of steps in a synthesis
Improves the atom economy
Reduces the amount of heat energy required
Easier separation methods
Enzymes can be reused
Uses less toxic solvents
Fewer organic solvents used
Reduces use of more toxic catalysts
```
114
Why is a polymerisation between an oyl chloride and an amine group a condensation?
A small molecule (HCl) has been eliminated (formed)
115
Why is a diol more environmental than an oyl chloride to undergo condensation reaction with a di amino?
Water rather than HCl is forms int the reaction which is toxic, needs to be disposed of
OR Oyl chloride contains chlorine which required extra energy, resources, to make
116
Strongest imb in polyethene
Instantaneous dipole indicted dipole
117
Strongest imb in Stanly
- NH
- COC
H bonding
118
Why does polyethene soften at much lower temp than Stanyl?
Imb in polythene are weaker than those in Stanyl
Less energy Needed to break the imb in polyethene and enable chains to slide
Chains can move over each other and polymer softens
119
E/V for H2/H+ half cell
0
120
Explain why the acid reacts with zinc but not copper. What is the oxidising agent?
Zinc -0.76
Hydrogen - 0
Copper + 34
Oxiding agent : H+
E standard values are measured with respect to H2/H+ half cell which = 0
Therefore, metals with e negative electrode potential value will be oxidised by H+ ions.
121
EDTA has what charge?
4-
122
EDTA4- is what dentate?
Hexadentate
123
What shape will EDTA4- ligands always be?
Octahedral
124
What will the coordination number of EDTA4- always be?
Coordination number 6
125
Copper II complex ion formed with EDTA4-
[Cu(EDTA)]2-
+2 and -4
-2 total
126
Alcohol to aldehyde
| Reagent and conditions
Acidified dichromate
| Distilled
127
What happened if you don't obtain an aldehyde?
Reflux
Excessive heating
Took place
Excess acidified dichromate was used
Acidified dichromate was not added slowly
Alcohol and aldehyde were oxidised further
128
Ester
R-COO-R
129
Ether
R - O- R
130
Ethanol plus ethanoic acid
C2H5OH + CH3COOH --> CH3COOC2H5 + H2O
131
Esterification conditions
| Ethanol and ethanoic acid
Concentrated H2SO4 which acts as a catalyst ( absorbs water)
132
Industrial enzyme pros
| To prepare organic compounds
Reduces number of steps
Increases atom economy
Could be cheaper, faster, reused, carried out at lower temperatures, reduces energy requirement
133
Some people lack an effective enzyme to convert ethanal to ethanoic acid
Enzyme less effective as a result of damaged DNA. Alternation of bases.
Enzymes are proteins which a specific sequence is amino acids
If the DNA is damaged, the primary structure of the protein will be altered: the sequence of amino acids in the enzyme will be altered
So the tertiary structure, folding of acids, of the enzyme will also alter
The active site is part of the tertiary structure and is where the reaction with the substrate takes place
An altered active site will not have the correct shape, cannot bind and interact with substrate by forming the correct intermolecular bonds
Substrate cannot bind with active sites
Cannot form substrate enzyme complex
By hydrogen bonding differently
134
Tg below room Temp
Will be flexible
Enough energy to break imb
Chains move/slide over each other
135
Tg above room temperature
Brittle
Not enough energy to break imb
Chains cannot move over each other
136
Adding an extra methyl side group alters flexibility
Chains cannot move over each other easily
137
Addictive to make polymer more flexible
Plasticiser
138
Make polymer more crystalline
Cold drawing
139
Ester hydrolysis conditions
Concentrated acid/ H+ (aq) and water
| Heat under reflux
140
Why are addition reactions environmentally friendly?
High atom economy (100%)
| Few/No waste: few/no atoms wasted
141
:CN- acts as what in mechanisms?
| Attached to Carbon chain by a C-C, not C-N
Nucleophile
| The lone pair of electrons which attack the electron deficient Carbon, not the N
142
H2C=CH3R
| E/Z isomerism?
No
| There aren't two different groups on each carbon
143
Explain why phenol group compound is able to dissolve with little aqueous alkali
Phenol group will react with alkali and form ion
| Ionic substances are more soluble in water
144
- phenol
- NH2
Plus HCl
- Phenol - no change
| - NH3+Cl-
145
- phenol
- NH2
Add ethanyol chloride
- Ethanoate group in stead of hydroxyl group in phenol
| - NHCO
146
Suggest the reducing agent responsible for the decrease in concentration of potassium manganate (VII) storage in sealed bottles.
Water
in dilute aqueous solution conc decreases due to a redox reaction taking place in sealed bottles. Oxygen is also formed in the reaction.
147
Unknown concl postassium manganate
| Standardise against sodium ethanedioate
Fill burette with MnO4- solution (unknown c)
Use graduated pipette for sodium ethanedioate (known c) to place solution in beaker
Then add MnO4- solution slowly near the end point until there is a permanent pink colour (pale purple)
148
D block catalysis
| E.g. cu2+
Reacts with one of the reactant to form an intermediate compound
Oxidation state of the transition mental ion changes
New ion/intermediate then reacts to form original transition metal ion
Therefore activation Enthalpy for this reaction is lower than without the transition metal ion
149
Aqueous transition metal ions : catalysis type?
Homogeneous
150
Why did the student use initial concentrations of C2O42- and H+ that were much larger than MnO4-
So during the reaction only the [MnO4-] would be effectively changing.
concentrations of C2O42- and H+ would be effectively constant.
151
First order half life
Constant
152
Copper electron configuration
3d10 4s1
153
Cu2+ electron configuration
3d9
154
Explain why copper is a transition metal
Cu forms an ion with partially filled set of d orbitals.
155
Protecting copper from corrosion
Barrier protection: galavanising, paint, grease, which prevents copper reacting with oxygen and water
Sacrificial protection
Coat with strap on blocks of Mg or Zn, galavanising
The more reactive Mg or Zn corrodes instead of Cu
156
Why does iron prevent copper form corroding
E standard value for Fe2+/Fe is more negative than that for Cu2+/Cu so Fe reacts and corrodes instead of Cu
So Fe reacts/corrodes instead of Cu
(Stronger reducing agent)
157
Crystallinity
How polymer chains are packed together
In an orderly, regular way
How polymer chains are aligned (lined up)
158
Above Tm
Polymer melts and becomes liquid
159
Below Tg
Polymer becomes brittle because chains cannot move over each other
So break when a force is applied
Blended polymer is more crystalline so imbs are stronger
More energy is needed to separate chains and melt polymer
160
Polymer form corn starch
| 'Green'
Manufactured from a renewable source
| Not manufactured from oil/ natural gas
161
Roasting the chromite ore with sodium carbonate in a air produces gas X
CO2
162
The Elements oxidised
Electrons lost
Fe+2 to Fe+3
Cr+3 to Cr+6
163
Na2CrO4
Sodium chromate (VI)
164
Removing a solid from solution
Filtration
| Centrifuge
165
Fe 3+ oxidising power Vs. Cr3+
| Method of extraction from ore
Fe +3 has a greater oxidising strength
Can be reduced by Carbon
The ?pure iron can be made from its ores by Carbon reduction.
166
Full labels for half cells
Pt electrode for non mentals
Inverted tube, for H2 to be pumped in at top
Voltmeter attached to electrodes
Salt bridge labelled
Standard conditions: 1moldm-: and 298K/25'C
167
Three ligands
Bi dentate
Coordination number?
6
168
Bond angle in octahedral
90'
169
*Bidentate ligand
It can donate two lone pairs of electrons
| To form dative covalent (Co-ordinate) bonds with metal cation.
170
Explain an acid base equilibrium
Transfer of a proton
| A prom is donated and accepted
171
Electronegativity
Ability of atoms to attract electrons in a covalent bond
172
Why is Fe2+ a stronger oxidising agent than Cr3+
Fe2+ is a stronger oxidising agent than Cr3+ because the Estandard of Fe3+/Fe half cell is more positive than that of the Cr3+/Cr half cell
173
Proteins to amino acid reaction
Condensation
174
Give the chemical reagent and conditions used in the lab to break down casein into its constituent amino acids
Peptide hydrolysis
Reagent: concentrated HCl
Conditions: heating under reflux
175
Tertiary structure
Overall folding of the protein
| The 3D shape
176
Tertiary structure affected by pH
| Use example groups
Changing pH affects the charges on groups
By lowering pH
- COO- can be protonated to form COOH
- NH2 print anted to NH3+
177
Why was a back card placed behind the tissues
| Milky, white to colourless
To help judge the si appearance if the suspension/ milliners
178
Rate v temp
| Roses then falls sharply
As the temp increases
Particles have more energy
More collisions have energy grater than the activation Enthalpy
Graph falls because at high temperatures intermolecular bonds break.
Loss of active site - its shape changes
179
When substrate concentration is high, what is its order?
Zero order
| All active sites are full
180
Problem chemists solve when a suitable dose of the oil for a diabetic patient
Oil - doesn't dissolve
Skin irritant
Dose which is safe
Find out which dilution is Non irritant
How to dissolve, administer oil - how to form a suspension of the oil
181
Thin-layer chromatography
Draw a pencil line at bottom of plate and place a drop of mixture and drop of each of the 3 compounds On the line
Place plate In solvent, line above solvent level, and add lid/ cover
When solvent nears top of the plate, remove , dry, plate
Locate spots with UV light, iodine
Compare heights of spots from mixture with the three standard compounds
Or Calculate Rf values of spots and compare those with standards.
182
Phenol and NaOH
Phenol reacts
To form salt
Soluble
No phenol In linalool so no reaction
Alcohols do not react with NaOH
183
C= O reduction
C-OH
184
Calculating solubility : mass in grams that will dissolve in 1.00 dm^3 at 25'C
Proportional to moles of H+
| gmol-1 X mol = g that will dissolve
185
Combinatorial chemistry
A method for synthesising a large number of similar organic compounds (analogues) in a short time
'Make a larger number of related compounds together quickly'
186
Esterification
| Type and co-product
Condensation
| Water
187
Polyester imb
```
Pdpd
Idid (as does everything)
```
188
Alkali hydrolysis
| Why Reflux
Vapours are condensed and turned to liquid
Mixture needed to be heated for a long time to break down polymers, reaction to occur
No reactants or products (vapours) lost
High temp required for reaction
189
Recrystallisation solvent proprieties and process
Dissolves salt well at high temp but very little or none at room temp
Use hot solvent
Dissolve in miminum amount of solvent
Leave or recrystallise
Filter off crystals so soluble impurities are left in filtrate, solution
Wash with cold solvent and dry
190
Explain why a substance produces a spectrum showing absorption peaks when irradiated with infrared frequencies.
Bonds in molecule absorb specific IR wavelengths.
Absorbing different frequencies causes different bonds to vibrate.
191
Tg
Temp below which the polymer turns glassy, brittle
192
PET
Tm 260'C
Heat to 300'C
It would melt - turn to liquid
193
A less crystalline polymer
Chains are further apart
So weaker intermolecular bonding
So chains Can move over one another more easily
194
C2O42- ( bidentate) ligands and Fe3+
Complex ion formed has change 3-
Coordination number
Shape
[Fe(C2O4)3]3-
3+,2-
3+ + -6 =3-
3+ + (2-x3) =3-
3 ligands, but bidentate
Coordination number 6
Shape : octahedral
195
Feasibility of Redox reaction using E cell
E standard electrode potential of ... is more negative than that of ...
E cell is +1.26 V so reaction is feasible.
196
```
Titration
Conc. Ethandioate solution can be found by titration
Standard postassium manganate (VII)
Acidic conditions
Slow at room temp.
Needs to be heared at 60'C
```
Manganate (CII) solution in burette
Pipette known volume of ethanedioate solution into flask
Add acid
Warm solution to 60'Titrate Until pink colour persists (because MnO4- unreacted being added and is in excess)
No indicator needed because only MnO4- (aq) is coloured. Or a colour change takes place during the reaction.
197
Progress of this reaction
Pink colour fades
Colour effervescence
Titration or colorimetry
198
Zwitterion
Forms a negative and positive charge
199
Changes in reaction rate during progress of reaction?
Colour change explained
Catalyst?
```
MnO4- purple to Mn2+ colourless
Mn2+ act as a catalyst
As reaction progresses
Rate increases
Catalyst is formed
Rate decreases as as reactants are used up.
```
200
Zwitterion with a phenol group in an aqueous solution
Acidic, alkaline , or neutral solution?
Acidic because it has a phenol group
201
Suggest why only one stereoisomers is effective in treating the disease
They have different shapes
| Only one will bind to receptor, active, site
202
DOPA has many adverse side effects
| Suggest why it is still used to treat pArkinson's
Benefits outweigh side effects
| It is more effective than other drugs, less adverse side effects
203
Titration
25.0 in pipette
Originally in 100 cm3 solution
Moles of original solution compared to titration?
Moles x 4
204
Overall order
The powers in rate equaton added
Rate = k X [] x[]^2
Overall order = 3
205
Alcohols to aldehyde
Acidified dichromate
| Add reagent to alcohol and distilled off aldehyde as it is formed
206
Rds
Slow step
Species in are in rate equation
The number of moles indicate the order
1 mole means first order, two moles means second order
207
Half equation formation Fe II ions
Fe-->Fe2+ + 2e-
| Oxidation
208
Ionic equation
Formation green rust
Fe II
Fe2+(aq) + 2OH-(aq) --> Fe(OH)2(s)
| (Ionic) precipitation
209
Oxidation red brown rust
+3
210
Why would green rust form instead of red
Why Fe II vs Fe III
Low oxygen Concentration around pipes
211
Green rust on a steel surface can be removed by converting the rust into a soluble iron compound
Rub surface with sulphuric acid
Compound formed ?
```
Iron (II) sulphate (VI)
Fe(2+)
SO4(2-)
O4=-8
S in SO4(2-) =+6
-8+6=2-
```
212
Complex
Central metal ion (cation) bonded to ligands (negative molecules)
213
Ligand
Molecule which has a lone pair which forms a dative covalent coordinate bond
214
Polydentate
A polydentate ligand can form more than one bond, donating at least two lone pairs to central atom, ion
Has more than one atom with a lone pair which are used to bond.
215
Possible shapes of complexes with four coordinate bonds
Square planar
| Tetrahedral
216
25 cm3 solution in grams
25 g
217
Colorimetry
Mix a fixed volume of B with a constant volume of each NaOH solution
Zero calorimeter
Use suitable filter of complementary colour
Measure absorbance of sample at known times/over time
Dilute H by known amounts
Measure absorbance
Plot graph of absorbance against [B]
[B] v absorbance
To get linear relationship
Confirm proportional
218
How would student do this.
| Determine order with respect to concentration B
Vary concentration of B
| Keep cocnetrai m of NaOH/OH- constant
219
How can one acid be polymerised
It has two functional groups which can react
New functional group is an ester
Condensation polymerisation
220
Polymer from glucose
| Advantage food packaging
Biodegradable, breaks down in soil
Renewable, sustainable source
Avoids use of fossil fuels (not made from crude oil)
221
Tg
Temp below which an polymer becomes brittle, glassy
222
Above Tg
Polymer becomes flexible, will bend because chains can slide over each other
223
PPO (With Tangled chains)
| Tg higher
Has tangled chains which need more energy to slide over each other
Tangled, less ordered chains cannot move, slide, over each other easily across each other
224
Explain this difference in garment stretch in terms of Imb
| bullet proof
Chains are straighter
So chain molecules are closer together
Imb between chains will be stronger
( polyamides - so H bonding )
225
Polyamides
H bonds
Pd-pd
And idid
226
Adding COCl to a compound
Acylation
| Elimination
227
Give a chemical reason why arsenic might be able to replace phosphorus
As and P are in the same group in the periodic table
| Both have five electrons in outer shell
228
Suggest a formula of H2AsO4- in strongly acidic solutions
H3AsSO4
229
Amine groups have basic properties
N atom has a lone pair of electrons
| Which can accept a proton/H+
230
Amide
NHCO
231
Better water absorption polymers
Form more H bonds
232
Polyester
pdpd
| Idid
233
Polymers with same linkage can have different strengths
Longer chains
More imb in longer chains
Polymer chains closer
Intermolecular bonds are stronger
Shorter monomer chains
More imb between chains
234
Adding recycled steel
Lower controlling temperature of contents of furnace
Absorbs heat
Prevents getting on hot: thermal shock
235
Suggest a modification chemists might make to structures of medicines to make more effective
Change functional groups
236
Thin layer chromograph material
plate/ sheet
Not 'paper'
237
Iron II to iron III by oxygen
Sodium hydrogen carbonate non return valve
Iron II to iron II can be oxidised by oxygen in the air
NaHCO3 reacts with acid to form CO2
Air/gas dispelled which cannot return
238
DNA fingerprint- ownership?
| Follow specific question stem
Choose to have stored
To find out about relatives, ancestors
To diagnose illness
Required to give DNA sample
They are criminal suspects
Choosing to have data removed
Infringes privacy
They have been found not guilty
239
Adenine-thymine and guanine-cytosine base pair bonding pair differences
How the specific paring suggests a copying mechanism for the replication of DNA
Adenine bonds to thymine with two hydrogen bonds, whereas guanine bonds to cytosine with three hydrogen bonds.
These hydrogen bonds break during DNA during DNA replication,.
Two single stands are formed.
Each base on these strands forms H bonds to new complementary base
240
Explain the effect of increasing pH has on the structure of the part of the protein formed.
- COOH will lose proton and form carboxylate ions, -COO-
| - No NH2+ or NH3+
241
Explain why the -OH group has acid properties in carboxylic acid, but not alcohol
The ion formed from carboxylic acid is more stable than the ion formed from the alcohol, because the in alcohol ion e.g ethoxide ion the negative charge is located on the oxygen, but in th carboxylic acid, Ethanoate ion, the charge is spread over the CO2- group
As the ion formed from ethanoic acid is more stable, the position of equilibrium moves to the right (products) and therefore a high concentration of H+ is present and ethanoic acid is more acidic
242
Why Phenol is more acidic than ethanol
The phenoxide ion is more stable than the ethoxide ion because the negative charge is spread, delocalised, into the benzene ring,
Whereas the ethoxide ion charge is located on the oxygen
As the phenoxide oxide ion is more stable, the position of the equilibrium,lies more to the right (products)
C6H5-OH --> C6H5O- + H+
Therefore a higher [H+] is present which means phenol Is more acidic
243
Vacuum filtration
Hirsch filter funnel, sintered disc
Buchner funnel, filter paper, Sintered disc
For separation of a solid rapidly from the solution, the filtrate
244
Fe(OH)2
Fe (OH)3
[Fe(H2O)6]2+
[Fe(H2O)6]3+
Colours?
Fe(OH)2 - GREEIIN
Fe (OH)3 - RED
[Fe(H2O)6]2+ -GREEIIN
[Fe(H2O)6]3+ - YELLOW/BROWN
245
[Cu(H2O)6] 2+
[Cu(NH3)4]2+ or [Cu(NH3)4(H2O)2]2+
Cu(OH)2
[CuCl4]4-
Colours?
[Cu(H2O)6] 2+ - BLUE
[Cu(NH3)4]2+ or [Cu(NH3)4(H2O)2]2+ - ROYAL BLUE
Cu(OH)2 - PALE BLUE
[CuCl4]4- - YELLOW
246
[Co(H2O)]2+
[CoCl4]2-
Colours?
[Co(H2O)]2+ - PINK
| [CoCl4]2- - BLUE
247
Nylon naming
Nylon-6,4
Nylon - (no. C in diamine),(no. c in dioic)
Nylon - 6,4
6 C in the diamine monomer and 4C the dioic monomer
Alphabetical - amine first, carboxylic acid second
248
Alkyl groups on amino acid naming order
Alphabetical order as always
249
Suitable locating agent for amino acids in chromatography
Ninhydrin
250
Kevlar properties
| Poly aromatic amide or 'aramid'
```
Fire resistant
Extremely strong
Can be made into flexible fibres
Highly crystalline
Low density
Resistant to chemical attack
Does not corrode
20 X stronger than steel of same mass
Chains are flat because of benzene ring
Chains are held together by H bonding
Rigid, ordered polymer molecules - maximises H bonding
```
251
Peek properties
Poly ether ether ketone
Halogen arene
High melting point
| Resistant to oxidation
252
Green chemistry in manufacturing polymers
```
Recycling
Producing energy
Producing chemical feedstocks
Degradable polymers
Minimising hazardous waste during raw material production and resulting polymers
Decreasing Carbon emissions
```
253
Degradable polymers
Biopolymers are made by living organisms and broken down by bacteria
Synthetic biodegradable polymers are broken down by bacteria
Photodegradable plastics
Broken down by sunlight
254
Keeping track of composition of steel in BOS process - basic oxygen steel making
Ionic emission spectroscopy
Steel made into electrode
Each element present emits a characteristic line spectrum, the intensity of lines proportional to atom conc.
255
Recycling polymer pros
Conserves fossil fuels feedstock
Reduces energy consumption
Reduces need for expensive landfills - plastics do not decompose readily when buried, limited spaces to fill
Reduces CO2, NO, and SO2 emissions caused by burning plastics
256
Recycling polymer cons
The plastics have to be sorted
| This is a very expensive process
257
How are polymers recycled?
Chemically
conversion back to monomers (depolymerising)
Only practical with high quality, single material waste - not co-polymers, works for some polyesters and polyamides
By cracking
Polymer is broken into smaller molecules which are used as feedstock in the chemical industry
By chemical recycling
Sorted into polymer type expensive manually, IR, X-Ray. Then melted, shredding, granulating, of waste plastics.
Is burning an option?
Impact on environment
Harmful emissions, such as toxic gases, and smoke/ash
However Incinerators can be used which generate heat and power but tech need to be developed to trap harmful emissions
258
High positive numbers of electrode standard potential means
Strongly oxidising
| Gain electrons
259
High negative numbers for electrode standard potential means
Strongly reducing
| Lose electrons
260
Feasibility of REDOX reactions
Construct electrode potential chart
Use it to make predictions about whether a reaction could occur
Use the half equations to give overall reaction
E electrode cell potential value - the more positive, the more feasible.
261
Polymer chain length
The longer, the stronger, increases points of contact
262
Polymer side groups
Polar side groups
e.g. Cl in PVC
Stronger bonding - pdpd
263
Polymer branching
Straight, unbranched, polymers pack together more closely
Increases points of contact
Stronger
264
Stereoregularity
Packing is more closely if side branches are arranged regularly e.g. Poly(propene)
Stronger imb
265
Chain flexibility
HC chains flexible
| Many orientations
266
Benzene in polymer
Increases rigidity
| Increases strength
267
Cross linking in polymers
Linked by covalent bonds
Makes polymer harder
More difficult to melt
Thermosetting
268
Longer chains
```
Stronger polymers
More point contact, closer packing, stronger imb
Increases tensile strength
More tangled together
Increases difficulty for sliding
Less flexible
```
269
Crystalline polymers
Polymers with extensive crystalline regions
More ordered, closely aligned
No bulky side chains or extensive branching
Regular chain structure
```
Increase in crystallinity
Increase in strength
Decrease in flexibility
Increases packing closely
Increases imb
Decreasing sliding, increase rigidity
```
270
Amorphous polymers
Opposite of crystalline
Increases flexibility decreases imb
Decreases close packing
Increases sliding
271
Flexibility
Depends on sliding
272
Why recycle steel?
Saves energy
Digging and extracting new ore needs a lot of energy and generates pollution
No need to dispose into landfills
Reduces waste
Aerosols need special facilities - dangerous if not completely empty
273
How is steel recycled?
All steel packaging can be recycled, except aerosols
Cleaning by incineration
Magnetic properties help sorting
Composition of new steel easily adjusted
Scrap steel is used to reduce temperature - acts as a coolant (absorbs heat), added to the converter before the molten iron is poured in to help reduce thermal shock
