Trials Flashcards
(131 cards)
1
Q
AAS definition and process
A
Using atomic absorption spectrometry (AAS) a sample solution containing an element is vaporised in a hot flame. Radiation from a cathode lamp of a particular wavelength is absorbed by the atom’s electrons. Unabsorbed light is passed through a wavelength selector and a detector. A computer determines the amount of absorbance as a measure of the concentration of the metal ions present in the sample.
2
Q
Production of alcohol
A
-Substitution reaction of haloalkanes with hydroxide (OH⁻)
-Fermentation of sugar/carbohydrates
3
Q
Oxidation of alcohols (each degree)
reagent
A
Primary - First to aldehydes then to carboxylic acids
Secondary - Ketones
Tertiary - Don’t Oxidize
H⁺/Cr₂O₇²⁻ (acidified dichromate)
H⁺/MnO₄⁻ (acidified permanganate)
4
Q
condensation equation
A
Alcohol + Carboxylic Acid→ Ester + Water
5
Q
4 types of addition reactions
A
Hydration, Hydrogenation, Hydro-halogenation and Halogenation
6
Q
Common ion effect
A
The solubility of a salt is reduced by the presence of one of its constituent ions (the common ion)
already in the solution. The presence the common ion drives the equilibrium towards
precipitation through Le Châtelier’s principle
7
Q
Fermentation of alcohols conditions
A
- Enzyme zymase (found in yeast)
- Warm temp (30-40C)
- Anaerobic (absence of oxygen)
- Aqueous solution
8
Q
Fermentation of glucose equation
A
C6H12O6 –> (zymase) 2C2H6O +2CO2
9
Q
Arrhenius definition and equations
A
Acids: dissociate in water to produce hydrogren ions
HCl(aq)→H+(aq)+Cl−(aq)
Bases: dissociate in water to produce hydroxide ions
NaOH(aq)→Na+(aq)+OH−(aq)
10
Q
Arrhenius adv with equation
A
Explains neutralisation, proposing hydrogen and hydroxide ions forming water
HCl(aq)+NaOH(aq)→NaCl(aq)+H2O
11
Q
Arrhenius disadv with equations
(3)
A
- Compounds without hydroxide ion displaying basic properties like metal oxides and metal carbonates
2HCl(aq)+CaCO3(s)→CaCl2(aq)+H2O(l)+CO2(g) - Neutrally charged salts like ZnCl2 being acidic in solution, whilst others are basic like Na2S
- Acid-base reactions that do not occur in aquous solution
NH3(g)+HCl(g) ⇋ NH4Cl(s)
12
Q
Bronsted Lowry definitions with equations
A
Acids; proton donors
HCl(aq)+H2O(l)→H3O+(aq)+Cl−(aq)
Bases: proton acceptors
NH3(aq)+H2O(l)⇋NH+4(aq)+OH−(aq)
13
Q
Bronsted Lowry advantages with equations
(4)
A
- substances that do not contain hydroxide ions.
- role of water as more than just a solvent.
- include solvents other than water and reactions in non-aqueous states.
- conjugate acid-base pairs.
HF(aq)+H2O(l)⇋H3O+(aq)+F−(aq)
NH3(aq)+H2O(l)⇋NH+4(aq)+OH−(aq)
14
Q
Bronsted Lowry disadv
A
- not explain the acidity of acidic oxides like SO2 and SO3
- not explain the basicity of basic oxides like MgO and CaO
- not explain reactions of acidic and basic oxides not involving proton transfer.
SO3(g)+CaO(s)→CaSO4(s)
15
Q
Methyl orange range
A
3.1-4.4
16
Q
Bromothymyl blue range
A
6.0-7.6
17
Q
Phenophalein range
A
8.2-11.0
18
Q
Cobalt chloride equilibrium equation (with colour changes)
H value
A
Co(H2O)6 2+ (aq) + 4Cl- (aq) <–> CoCl4 2- (aq) + 6H2O (l)
pink —————– blue
endothermic
19
Q
Iron (III) thiocyanate equilibrium equation (with colour changes)
H value
A
Fe3+ (aq) + SCN- (aq) <—-> FeSCN 2+ (aq)
yellow—colourless——blood-red
exothermic
20
Q
H: -
S: +
A
spontaneous
21
Q
H: +
S: +
A
spontaneous if T is high
22
Q
H: -
S: -
A
spontaneous if T is low
23
Q
H: +
S: -
A
non-spotaneous
24
Q
What is favoured in terms of collision theory temperature increases
A
If endothermic reaction: reverse favoured
If exothermic: forward favoured
(less energy needed to surpass activation energies)
Endothermic reactions have higher increase in reaction rate due to low value?
25
VALIDITY
Aim
Constant
Equipment
Range
26
RELIABILITY
Repeated
Outliers
Consistent
Aveaged
27
ACCURACY
Scale
equipment
Rrecorded
Close to therorital
28
Catalyst effect
Lower activation energy
Increased reaction rate for fwd and rvs
29
Inert/unreactive gas effect
no effect, lowers rate of rxn for both sides
30
Detoxyfying cycads
Leaching: use of water to dissolve the toxin and remove it from the plant
"When the seeds are soaked in water (e.g. a river or creek), the flowing water reduces the concentration of aqueous cycasin, disturbing the equilibrium. According to Le Chatelier's principle, the equilibrium will shift right to produce more aqueous cycasin and minimise the disturbance, hence increasing the rate at which cycasin dissolves."
31
Buffer region of titration curves (explain)
OH- and H+ react
Little change occurs since OH is in excess at the start (or other way around)
32
strong acid strong base titration curve
(eq point range, indicator to use)
4-10
all 3 (or bromothymyl blue)
33
strong acid weak base titration curve
(eq point range, indicator to use)
3-7
methyl orange
34
weak acid strong base titration curve
(eq point range, indicator to use)
7-11
phenophalein
35
Conductivity rules
OH and H have the most mobility and create an electrical current
Curve decreases as OH and H react and conductivity is held by Na which has low conductivity
36
Which conductive curve is the non-straight round one?
Weak acid strong base
37
Which conductive curve is the one that increases at the start?
weak acid weak base
38
Why is it that in a weak base and weak acid conductivity curve, it increases at the start?
Acid and base molecules react to become ions (acid donates H+)
More ions means more conductivity
39
Carbonic buffer system in blood equation
Why is it there
pH range
Alkalosis and acidosis
Ions it is between
H2CO3 (aq) + H2O (l) <---> HCO3 - (aq) + H3O+ (aq)
Controls how much H+ and OH- in cells, tissues
Importance for metabolic processes and enzymes to function
7.35-7.45
Alkalosis: hyperventilation, low levels of CO2
Acidosis: diseases
H2CO3 and HCO3 -
40
What type of combination do you need for a buffer?
WEAK acid/base and conj
Large conc for better capacity
Equal moles/conc
41
Ketone and aldehyde oxygen placement
Ketone: middle
Aldehyyde: end
42
Hydrocarbons with distinct smells
Amine (ammonia, fishy), esters
43
Polarity rule (lone pairs for amine)
The presence of lone pair of electrons causes repulsion, and thus it affects the bond angle. Thus, it can increase or decrease the polarity of a molecule.
44
Hierarchy of boiling points (lowest to highest)
alkane, amine/aldehyde, ketone, alcohol, carboxylic acid, amide
45
how are esters and amides produced
condensation reactions
46
Reliability
the consistency of experimental results over mutiple trials under the same conditions
47
Validity
the extent to which the aim of the experiment is fulfilled fairly
48
Accuracy
the closeness of agreement between an experimental result and the accepted theoretical value
49
Petrol
How is it produced?
Chemical composition?
Combustion equation?
Fractional distillation of crude oil. Catalytic cracking of larger fractions from crude oil.
Hydrocarbons like octane and heptane
C8H18(l) + 25/2 O2(g) --> 8CO2(g) + 9H2O(l)
50
Petrol
Enthaply of commbustion?
Source?
Renewable or non?
CO2 emissions?
Vehicle modification?
48kj/g
Crude oil
Non-renewable
High net release during production and use
None
51
Petrol
Running costs?
Environmental impacts
Depends on the price of petrol at the time! Sometimes more expensive than ethanol, sometimes not
Mining, accidents, net release of CO2 higher than biofuels, oil spills
52
Ethanol
How is it produced?
Chemical composition?
Combustion equation?
Fermentation of glucose from biomass (plant sugars) and/or hydration of ethene
ethanol
C2H5OH(l) + 3O2(g) --> 2CO2(g)+ 3H2O(l)
53
Ethanol
Enthaply of commbustion?
Source?
Renewable or non?
CO2 emissions?
Vehicle modification?
29.6 kj/g
Biomass/sugar cane/ molasses
Renewable
Lower net release during combustion since recently removed from atmosphere through photosynthesis
if under 10% no modification needed
54
Ethanol
Running costs?
Environmental impacts
Depends on the price of petrol at the time! Sometimes more expensive than petrol, sometimes not
Growing sugarcane to provide sugar uses a lot of land that could be used for food production. Better if using leftover biomass
55
Biodiesel
How is it produced?
Chemical composition?
Combustion equation?
From plant oils such as soybean, corn, palm oils.
Esters made from fatty acids of oils
Ester + oxygen --> CO2 + H2O
56
Biodiesel
Enthaply of commbustion?
Source?
Renewable or non?
CO2 emissions?
Vehicle modification?
37.2
Usually from waste oils from restaurants and industry.
Renewable
Some release associated with production
Diesel engine required. Up to 20% biodiesel mixed with ordinary diesel does not require modification
57
Biodiesel
Running costs?
Environmental impacts
Cheaper than regular diesel.
Using leftover oils reduces need to plant crops and use arable land specifically for production of biodiesel.
58
Molecular formula for alkane
C(n)H(2n+2)
59
Molecular formula for alkene
C(n)H(2n)
60
Molecular formula for alkyne
C(n)H(2n-2)
61
Molecular formula for alcohols
C(n)H(2n+2)O
62
Molecular formula for carboxylic acid
C(n)H(2n)O2
63
Molecular formula for aldehyde/ketones
C(n)H(2n)O
64
Endpoint
The point during a titration when the indicator first produces a permanent colour change and this indicates that equivalence point has been reac
65
What causes each colour change for H+/MnO4-
Original: purple (same ion)
MnO2 (s): brown ppt --> aldehyde
Mn2+ : colourless --> carboxylic acid
66
What are the colour changes of H+/CrO4 2-
Orange --> green
67
What are the oxidising reagents called
ACIDIFIED potassium permanganate
ACIDIFIED Potassium dichromate
68
What do fangs on a IR spec indicate?
n-H bonds (number of fangs=number of H's)
2 fangs: primary amide
1 fang: secondary amide or terminal alkyne
69
If the oxidation colour stays ornage that means...
Not a primary/secondary or aldehyde functional group (all oxidisable)
70
Words to use in HNMR spec
Terminal: at the end
Non-terminal environment
This hydrgen environment is adjecent to 3 hydrogens
Adjecent to CH2 group capable of this triplet splitting
71
Flame colours of each atom
Barium
Calcium
Copper
Lithium
Pottassium
Sodium
Apple green
Brick red
Blue green
Crimson red
Lilac
Yellow
72
Identification test
Cl-
Forms a white ppt with acidified Ag+ solution which dissolves in dilute ammonia to form a colourless complex
73
Identification test
Br-
Forms a cream ppt with acidified Ag+ solution which dissolves in concetrated ammonia to form a colourless complex
74
Identification test
I-
Forms a yellow ppt with acidifed Ag+ solution which does not dissolve in ammonia
75
Identification test
OH-
pH greater than 7 (turns litmus blue) or forms a blue ppt with Cu2+
76
Identification test
CH3COO-
Forms a red-brown complex when reacted with FeCl3
77
Identification test
CO3 2-
Forms bubbles when HNO3 is added and the gas turns limewater milky (CO2)
78
Identification test
SO4 2-
Forms a white ppt with either acidified Ba2+ or acidified Pb2+
79
Identification test
PO4 3-
Prodcues a yellow ppt with acidified (NH4)MoO4 (ammonium molybdate)
80
Identification test
Ba2+
Forms no ppt with F- (add NaF)
81
Identification test
Ca2+
Forms a white ppt with F- (add NaF)
82
Identification test
Mg2+
Forms a white ppt with OH-
83
Identification test
Pb2+
Forms a yellow ppt with I- (add NaI solution)
84
Identification test
Ag+
Forms a white ppt with Cl- which will dissolve ammonia, forming a complex
85
Identification test
Cu2+
Produced a deep blue complex with ammonia and water
86
Identification test
Fe2+
Decolourises acidified potassium permanganate solution
87
Identification test
Fe3+
Forms a blood red complex with SCN- (add KSCN)
88
Colourimetry process
a light source which produces light that is absorbed by the solution; this is passed through a filter to select a particular colour of light required for the analysis
* a transparent cell to hold the sample
* an electronic detector to measure the intensity of light that passes through the cell
* a recorder or electronic display that shows how much light was absorbed by the sample.
needs various standard solutions of the ion to test for different colourimetry
89
UV Vis spec (quantitative)
Colorimeters are cheap and can be used easily in school laboratories.
However, their accuracy is limited.
* UV-Visible spectroscopy is like a colorimeter, but has higher accuracy
* UV-Vis uses a monochromator rather than a filter to select light of an
exact wavelength to be used in the analysis.
90
What do safety precautions for hydrocarbons help do?
Prevent the buildup of vapours, reduces risk of fuel igniting
91
As carbon chain length increases...
more elecrons, stronger dispersion forces, increases mp/bp, overpowers other intermolecular forces
92
Ketone and aldehyde IMF and solubility
dipole-dipole
- as chain length icnreases, more dispersion forces decrease solubility (dipole dipole with water)
93
Special property about tertiary amides
Cannot hydrogren bond
94
Petrol
Environmental, eocnomic, social implications
Social: provides jobs and income
Economic: oil spills --> economic losses, ruin fisheries and fishing industry, USA Russia and Saudi Arabia have largest reserves, large oil industry
Environmental: mining (land degradation, habitat destruction, deforestation, oil spills, pollution of water ways
Fractional distillation: requires heat input which is burning fossil fuels (CO2 emissions)
95
Disadv of soap
Cannot be used in acidic conditions
Cannot be used in hard water -> forms soap scum with Mg and Ca ions
96
Events of removing grease using soap
Process
1. The non-polar ends of the soap ions bond to the surface of the grease via dispersion forces.
2. The ionic ends bond to water molecules via H-bonding/ion dipole interaction.
3. The grease on clothing or on skin is loosened by agitation or rubbing.
4. The non-polar ends of the soap ions surround more and more of the grease droplet as it is loosened from the surface by further agitation.
5. The result is a micelle, with a spherical shape -the grease droplet is surrounded by the non-polar ends of many soap ions, with the ionic ends bonding to water.
6. Thus, the grease is dispersed throughout the water in the form of an emulsion - the emulsion is the soap, water and grease mixture.
97
Anionic detergents
sulfonate head
uses: shampoos,
dishwashing detergents, washing
powders
forms soluabe complex with hard ions
98
catonic detergents
bonds to - charge -- reduce static
uses: hair conditioners, fabric
softeners, disinfectants.
99
non ionic detergents
not lather much
uses: Dishwashing detergents
Glass Cleaners
100
Esters IMF
dipole dipole
unable to hydrogen bond as they have no H directly connected to O
101
Qsp < Ksp
no ppt (high conc of ppt, so eq moves to right to produce ions)
102
Qsp > Ksp
yes ppt (high conc of ions, so eq moves to left to produce ppt)
103
Neutralisation examples
Agriculture: adding powdered lime, CaO, limestone to acidic soils
Industry: acid or base spills, netrualisating acidic emissions from factories or power plants
Heath: treating patients who have indigestion
Home: preventing tooth decay by neutralising acids, using baking powder in food preperation
104
Flame test explanation
When atoms are heated, the outer shell electrongs absorb energy and become excited, moving to higher energy levels. The atoms are unstable and the electrongs quickkly move back to a lower energy state, emitting energy as light of a specific wavelength and colour. If in the visible region, the flame appears an characteristic colour.
105
Limit of flame tests
Can only identify a few metal unambigously, because many flame colours are similar or are masked by colours of other metals that may be present
106
Complexation reactions
Form complex ion, usually involving trasition metals (Fe, Ag)
Consists of central metal cation surrounded by 1-6 bound polar molecules or anions (called ligands)
107
Steps of gravimetric analysis
1. Weight sample
2. Dissolve in solvent (water)
3. Add excess reactant to form ppt
4. Filter ppt and wash filter paper with water
5. Dry ppt in oven
6. Weight ppt sample
108
UV visible spec process
1. Standard solutions prepared
2. A wavelength is selected at which the component absorbs light strongly
3. Absorbance of the standard solution at that wavelength measured
4. Calibration curve graphed using conc of standard solutions
109
AAS
The sample is atomised in a flame. Electrons in atoms absrob light energy of specfic wavelengths, whih causes the elctrons to jump to higher energy levels. A hallow cathode lamp produces light in specific wavelengths that the metal atom can absorb. Wave length selector and detercter determines concentration by consutrcting calibration curve using absorbance.
110
Mass spectroscopy process
Electron beam removes electrons, creating cations. Presence of electric and magnetic field leads to cations moveing in curved paths dependent on mass/charge ratio (m/z)
Cation can be unstable. Some fragment, where one frgamnent is a cation, and other is an uncharged free radical (atom or group)
Cations are accelerated. y electric field and then deflected by magnetic field.
111
Infared spec process
Causes bonds to stretch (change distance between atoms) and bend (change angle between bonds), as their polar bonds interact with IR light.
Single bonds absorb less energy
112
NMR progress (nucleur magnetic resonance)
Interaction of nuclei of atom in a strong magnetic field with radio wave energy
Flips
113
Aim of chemical synthesis and design
Aim for high yield of a pure product that is produced quickly ad efficently at a marketable price, while ensuring the health and safety of employees and minimising damage to the environment
114
Points to talk about in chemical synthesis and design
Availability of reagents, reaction conditions, yield and purity, location, env soc econ issues
115
Industrial uses of ammonia (haber process)
Production of fertilisers
A cleaning agent
Production of other chemicals such as explosives and synthetic fibres
116
Availaibilty of reagents (haber process)
H2 is usually obtained from steam reforming of hydrocarbons
Steam reforming involves a reaction between natural gas and steam
N2 is from air
117
haber process equation
H value
N2 (g) + 3H2 (g) <--> 2NH3 (g)
exothermic
118
Reaction conditions of haber process
To increase yield:
decrease temperature (LCP favour forward exothermic and Keq increases)
increase pressure (LCP favor fwd)
To increase rate of rxn:
Increase T
Catalyst: porous Fe/Fe3O4
Temp must comprimise at moderate 350-500C, under 250atm (P)
119
Yield of haber process
NH3 is liquiefied for easy transport
Unreacted gases are recycled to achieve 98% yeild and reduce emissions
120
Waste management of haber process
Wasting energy --> use of hea exchangers, energy reused to preheat and generate steam during plant process --> less costs and more efficent
Production of CO2, NO2, SO2, CO in steam reforming --> liquidefy CO2, selling to food beverage fertiliser companies, monitering of emissiosn --> reduce enhanced greenhouse
Sulfur in natural gas for steam reforming produces SO2 (g) --> desulfurisation, collection of gas, sold as raw material for H2SO4 producution --> minimising acid rain, pollustion, poisining of catalysts
121
Health and safety in haber process
Ammonia= toxic gas, fire and explosions are hazards
Wear protective clothing, gloves, face shields, rubber boots, aprons, well ventilaited factories, breathing apparatus available
122
Primary standard conditions
High molar mass
Stable
Easily stored
Not reactive with water or atmospheric gases
Known chemical formula
Pure
Easily weighable
123
Why is AAS good for multiple ions
Looks at one particular wavelength of one element, in ppm
124
Nylon properties and uses
High tensile strength
Strong fribre, resistant to abrasions and moisture
Textiles, machine rubber and parts, rope, thread
125
ester to primary/secondary alchohol
NaOH and heat
126
dehydration of alchohol
conc H2SO4 and heat
127
Alkyne to ketone
H2O + H2SO4 + HgSO4
128
Alkyne or alkene to alkane
H2 + Ni
129
Haloalkene or alkene to alkane
HX or X2 + Ni
130
Haloakane to alcohol
NaOH + heat
131
