Module Eight - Applying Chemical Ideas Flashcards
Analysis of Inorganic Substances Analysis of Organic Substances Chemical Synthesis and Design (195 cards)
1
Q
what are the two sources of pollution?
A
- chemical spills
- fertilisers
2
Q
why is it important to monitor the environment?
A
- to see and analyze trends & patterns of the presence of pollutants in the environment
- to ensure the preservation of flora and fauna
3
Q
how do chemical spills affect the environment?
A
- consequences may be long-term if the chemicals cannot be contained
- can affect waterways and soil, making it dangerous to consume from
4
Q
how do fertilisers affect the environment?
A
- run-off may encourage algae growth (eutrophication)
- algal blooms will starve waterways of oxygen and light
- will destroy habitats
- no light or oxygen for fish and plants
5
Q
how do naturally occurring substances become pollutants?
A
when their concentrations exceed levels agreed to in regulations
6
Q
what method is best for identifying ions in solution?
A
precipitation
7
Q
when two solutions are combined and becomes cloudy, has a precipitate formed?
A
yes, particles are just in suspension
8
Q
how can precipitation reactions help with the environment?
A
can be used to remove unwanted substances from water
9
Q
what are the two main qualitative tests in identifying certain cations and anions?
A
flame test, precipitation
10
Q
why is it important to identify ions in the environment?
A
identify which substances are in dangerous levels which’ll pose danger
11
Q
what are examples of cations?
A
barium (Ba2+) calcium (Ca2+) magnesium (Mg2+) lead(II) (Pb2+) silver (Ag+) copper(III) (Cu2+) iron(II) (Fe2+) iron(III) (Fe3+)
12
Q
how do flame tests work?
A
- when heated, electrons in an atom will enter an excited state
- will jump to a higher energy level
- when it goes back down (ground state), energy is released in the form of light
- each atom has it’s own wavelength
13
Q
what is the flame colour of calcium?
A
orange-red
14
Q
what is the flame colour of barium?
A
apple green
15
Q
what is the flame colour of copper?
A
blue-green
16
Q
what is the flame colour of lead(II)?
A
light blue
17
Q
what is the flame colour of iron(II)?
A
gold –> blue-green –> brown
18
Q
what is the flame colour of iron(III)?
A
orange-brown
19
Q
are flame tests suitable for cations or anions?
A
cations
20
Q
what are complexation reactions?
A
involves the formation of complex ions
21
Q
what are complex ions?
A
when one or more small molecules or ions attach themselves to a central cation
22
Q
what is the central cation usually in a complex ion?
A
transition metal ion
23
Q
what are the small molecules/ions that attach to the central ion in a complex ion called?
A
ligands
24
Q
what do ligands usually contain?
A
at least one lone pair of electrons
25
what does the ligand in a complex ion act as?
electron donator
26
what is a coordinate covalent bond?
when all the electrons shared between two atoms come from the same atom
e.g. H+ and H2O --> H3O+
27
what is the bond between the central cation and ligand?
coordinate covalent bond (both electrons come from ligand)
28
what colour are copper(II) salts in solution?
blue
29
is a precipitate formed when NaOH is added to a solution containing copper(II) salts?
yes
30
what colour is the precipitate formed when NaOH is added to a solution containing copper(II) salts?
pale blue
31
what complex is formed when copper(II) salts are dissolved in water?
hexaaquacopper(II)
| [Cu(H2O)6]2+
32
what occurs during the complexation reaction between aqueous copper(II) and NaOH?
two of the OH- ions replace two water molecules (precipitate is formed)
[Cu(H2O)4(OH)2](s)
33
what are examples of anions?
```
chloride (Cl-)
bromide (Br-)
iodide (I-)
hydroxide (OH-)
acetate (CH3COO-)
carbonate [CO3(2-)]
sulfate [SO4(2-)]
phosphate [PO4(3-)]
```
34
what is the first step when identifying a cation?
addition of HCl
35
what is the first step when identifying an anion?
testing with red litmus paper
36
how is Pb2+ identified?
1. add HCl
2. white ppt is formed
3. add NH3
4. ppt does not dissolve
5. add iodide
6. yellow ppt is formed
7. identified!
37
how is Ag+ identified?
1. add HCl
2. white ppt is formed
3. add NH3
4. ppt dissolves
5. identified!
38
how is Ba2+ identified?
1. add HCl
2. no ppt is formed
3. add H2SO4
4. ppt is formed
5. flame test
6. lime green flame
7. identified!
39
how is Ca2+ identified?
1. add HCl
2. no ppt is formed
3. add H2SO4
4. ppt is formed
5. flame test
6. red-orange flame
7. identified!
40
how is Cu2+ identified?
1. add HCl
2. no ppt formed
3. add H2SO4
4. no ppt formed
5. add NaOH
6. blue ppt formed
7. add conc. NH3
8. royal blue ppt formed
9. identified!
41
how is Fe2+ identified?
1. add HCl
2. no ppt formed
3. add H2SO4
4. no ppt formed
5. add NaOH
6. green ppt formed
7. add MnO4-
8. decolourises
9. identified!
42
how is Fe3+ identified?
1. add HCl
2. no ppt formed
3. add H2SO4
4. no ppt formed
5. add NaOH
6. brown ppt formed
7. add SCN-
8. deep red colour
9. . identified!
43
how is Cl- identified?
1. test with red litmus paper
2. stays red
3. add AgNO3/dilute HNO3
4. ppt formed
5. add dilute NH3
6. ppt dissolves
7. identified!
44
how is Br- identified?
1. test with red litmus paper
2. stays red
3. add AgNO3/dilute HNO3 4. ppt formed
5. add dilute NH3
6. ppt does not dissolve
7. add conc. NH3
8. ppt dissolves
9. identified!
45
how is OH- identified?
1. test with red litmus paper
2. turns blue
3. add dilute HNO3
4. no bubbles
5. add Cu(NO3)2
6. blue ppt formed
7. identified!
46
how is CH3COO- identified?
1. test with red litmus paper
2. turns blue
3. add dilute HNO3
4. no bubbles
5. add Cu(NO3)2
6. no ppt formed
7. identified!
47
how is CO3(2-) identified?
1. test with red litmus paper
2. turns blue
3. add dilute HNO3
4. bubbles formed
5. identified!
48
how is SO4(2-) identified?
1. test with red litmus paper
2. stays red
3. add AgNO3/dilute HNO3
4. no ppt formed
5. add dilute HNO3 and Ba(NO3)2 [fresh sample]
6. ppt formed
7. identified!
49
how is PO4(3-) identified?
1. test with red litmus paper
2. stays red
3. add AgNO3/dilute HNO3
4. no ppt formed
5. add dilute HNO3/Ba(NO3)2 [fresh sample]
6. no ppt formed
7. add NH3 and Ba(NO3)2 [fresh sample]
8. ppt formed
9. identified!
50
how is I- identified?
1. test with red litmus paper
2. stays red
3. add AgNO3/dilute HNO3
4. ppt formed
5. add dilute NH3
6. ppt does not dissolve
7. add conc. NH3
8. no change
9. identified
51
what are the two methods of quantitative ion analysis?
- precipitation titrations
| - gravimetric analysis
52
what are the three methods of precipitation titrations?
- Mohr's method
- Volhard's method
- Fajan's method
53
what type of titration is Mohr's method?
direct titration
54
what type of titration is Volhard's method?
- direct titration for Ag+
| - back titration for anions
55
what type of titration is Fajan's method?
direct titration
56
what is Mohr's method used for?
- determination of chlorides, bromides & cyanides
| - titrated with a known concentration of AgNO3
57
what is a blank titration?
- a titration without an analyte being present
| - performed to see how much has been overshot by comparing colours
58
what indicator is used in Mohr's method?
chromate ions [CrO4(2-)]
| yellow --> red-brown
59
what is Volhard's method used for?
- to determine the quantity of particular anions in solution
| - can also identify Ag+
60
what indicator is used in Volhard's method?
```
thiocyanate ions (SCN-)
colourless --> blood red
```
61
what is Fajan's method used for?
end point is determined by a colour change in an absorption indicator
62
what indicator is used in Fajan's method?
multiple indicators for particular species
63
what species are analysed in Mohr's method?
Cl-, Br-, CN-
64
what species are analysed in Volhard's method?
Cl-, Br-, I-, CN-, PO4(3-), Cr2O7(2-), S(2-), CO3(2-)
65
what species are analysed in Fajan's method?
Cl-, Br-, I-
66
does gravimetric analysis rely on mass or volume?
mass
67
what is an example that gravimetric analysis would be useful in?
composition of fertilisers
68
how is the composition of fertiliser calculated gravimetrically?
1. fertiliser is dissolved
2. chemicals added to make ppt
3. solid ppt is filtered
4. ppt is dried and weighed
5. mass is compared to initial mass of fertiliser
69
what is a common element found in fertiliser that is usually calculated?
sulfate content
70
what chemical is usually used when used to ppt out sulfate from fertiliser?
barium chloride to make barium sulfate solids
71
what are the possible errors of gravimetric analysis?
- contamination with other species
- loss of sample from inefficient filtering, spillage, or rinsing of containers
- not all content is ppt out
- sample not completely dry
72
does contamination of other species during gravimetric analysis cause an overestimation or underestimation?
overestimation
73
does loss of sample during gravimetric analysis cause an overestimation or underestimation?
underestimation
74
does not all of the sample being precipitated out during gravimetric analysis cause an overestimation or underestimation?
underestimation
75
is the sample not being completely dry during gravimetric analysis cause an overestimation or underestimation?
overestimation
76
what are the six types of instrumental quantitative techniques?
- atomic absorption spectroscopy (AAS)
- ultraviolet-visible spectrophotometry (UV-vis)
- colourimetry
- mass spectroscopy
- NMR spectroscopy
- infrared spectroscopy
77
how does AAS work? (general)
uses the absorption of light by electrons in the atom to measure how much of an element is present in a sample
78
what is atomic absorption spectroscopy (AAS) used for?
used to determine the concentration of metal ions present in particular substances
79
what is the process of AAS?
1. light is pulsed out of the hollow cathode lamp
2. light goes through flames of burner
3. sample solution is sprayed on flame
4. goes through monochromator to select a wavelength
5. goes through photomultiplier to intensify weak signals
6. reading shown on output display
80
what are the parts of AAS equipment?
- hollow cathode lamp
- burner
- monochromator
- photomultiplier
- detector
- output display
81
what is the purpose of the hollow cathode lamp in AAS?
- lamp chosen is made of the same element being tested
| - light emitted has the wavelength of the element
82
what is the purpose of the burner in AAS?
- vapourises the sample
| - changes it to atoms (atomises)
83
what is the purpose of the monochromator in AAS?
selects just one wavelength of the light
84
what is the purpose of the photomultiplier in AAS?
multiplies weak signals
85
what is the purpose of the output display in AAS?
displays the quantitative result (intensity of light)
86
what is the purpose of the detector in AAS?
measures the intensity of the light
87
how is absorbance related to concentration on AAS?
more concentrated = more absorbance = lower absorbance VALUE
88
what is measured in AAS?
absorbance
89
is more or less light measured in a concentrated sample in AAS?
less
90
how is AAS quantitatively analysed?
analysed through a calibration curve
91
what is colourimetry?
method for determining the concentration of a chemical using its colour and concentration in solution
92
what is ultraviolet-visible spectrophotometry?
used for measuring radiation absorbed by a coloured species across multiple frequencies
93
what equipment is used in colourimetry?
colourimeter
94
how is colour intensity related to concentration?
they are directly proportionate
95
what are the parts in a colorimeter?
- bulb
- cover
- glass cuvet
- filter
- light sensor
- display
96
what is the process of colourimetry?
1. light from the bulb is passed through a filter
2. solution is placed in a glass cuvet
3. filtered light passes through solution
4. some light is absorbed
5. amount absorbed to measured
97
why must the filter be a complementary colour of the solution in colourimetry?
the colour of the solution is complementary to what has been absorbed
98
what is a glass cuvet?
a special type of test tube used in colourimetry
99
how is colourimetry quanitatively analysed?
through a calibration curve
100
what is a calibration curve?
uses known values in a graph to help make conclusions on results obtained
101
what is the x-axis label in a calibration curve?
concentration of element (ppm)
102
what is the y-axis label in a calibration curve?
absorbance
103
how can we test for carboxylic acid?
- blue litmus: turns red
| - add Na2CO3: CO2 bubbles form (turns lime water milky)
104
how can we test for an alkene?
- add bromine: decolourises
| brown --> clear
105
how can we test for an alcohol?
- add CaCl and Na(s): H2 bubbles form (will pop in pop test)
| - add KMnO4: changes from pink colour
106
what are the different types of waves in increasing wavelength order?
- x-rays
- ultraviolet rays
- infrared rays
- microwaves
- radiowaves
107
what is the relationship between wavelength and frequency?
inversely proportionate
108
what is the relationship between wavelength and energy?
inversely proportionate
109
what is the relationship between frequency and energy?
directly proportionate
110
what is the energy source for mass spectroscopy?
high-energy electrons
111
what is the energy source for NMR spectroscopy?
radiowaves
112
what is the energy source for infrared spectroscopy?
infrared waves
113
what is the energy source for UV-vis spectroscopy?
UV-visible waves
114
what data is received from mass spectroscopy?
- peaks correlating to the m/z ratio
| - shows molar mass and isotopic abundances
115
what data is received from NMR spectroscopy?
peaks that are useful for identifying the C-H backbone of a molecule
116
what data is received from infrared spectroscopy?
bands used to determine the type of bonds and functional groups present
117
what data is received from UV-vis spectroscopy?
shows the concentration of organic compounds
118
what is mass spectroscopy?
a process that measures the mass-to-charge ratio of charged particles
119
what is an advantage of mass spectroscopy?
only requires a small amount of material
120
what can mass spectroscopy be used for?
- radioactively dating fossils
| - detecting drugs in sport supplements
121
what are the four steps in mass spectroscopy?
1. ionisation
2. acceleration
3. deflection
4. detection
122
what occurs during the ionisation stage in mass spectroscopy?
- electrons are shot at the vaporised sample to knock off an electron
- makes it a molecular ion (radical)
123
what does NMR stand for?
nuclear magnetic resonance
124
what are the parts to the mass spectroscopy equipment?
- ion repeller
- electron gun
- electron trap
- electromagnet
- detector
- amplifier
125
what occurs during the acceleration stage in mass spectroscopy?
positive particles are accelerated along the path by an electrical field
126
what occurs during the deflection stage in mass spectroscopy?
- particles pass through a magnetic field, deflecting at an angle according to their mass and charge
- lighter particles deflect further
127
what occurs during the detection stage in mass spectroscopy?
intensity of the beam that makes it through hits the detector to be measured
128
what is the x-axis in a mass spectroscopy graph?
m/z (mass to charge ratio)
129
what is the y-axis in a mass spectroscopy graph?
relative abundance
130
what is the most important peak on a mass spectroscopy graph?
the parent molecular ion peak
131
what are the two peaks to analyse in a mass spectroscopy graph?
- base peak
| - parent molecular ion peak
132
what is the base peak in a mass spectroscopy graph?
the tallest peak
133
what is the parent molecular ion peak in a mass spectroscopy graph?
the peak with the largest m/z (most to the right)
134
what does the parent molecular ion peak tell us on a mass spectroscopy graph?
molecular mass of the parent molecule
135
what does the base peak tell us on a mass spectroscopy graph?
the most abundant fragment of the molecule
136
what are some of the common fragments in molecules to look for in a mass spectroscopy graph?
```
CH3 - 15
OH - 17
H2O - 18
CH2CH3 - 29
CHO - 29
OCH3 - 31
COOH - 45
OCH2CH3 - 45
```
137
what is a molecule requirement in order to undergo NMR spectroscopy?
only nuclei with an odd amount of NUCLEONS
138
why can only nuclei with an odd number of nucleons be used in NMR spectroscopy?
if even, the spins will cancel each other out
139
what two nuclei are most commonly used in NMR spectroscopy?
H1, C13
140
what piece of equipment is used in NMR spectroscopy?
- large magnet
- sample holder
- source of radio waves
- detector
141
what are chemical environments in NMR spectroscopy?
- nuclei are in the same environment when they are bonded to the same group of atoms in the same way.
- protons in the same environment will absorb the same frequency and produce one peak
142
what is the chemical shift in NMR spectroscopy?
- all peaks are relative to the most shielded compound, (towards the right)
- it is the 'zero' on the NMR graph
143
what is TMS?
tetramethylsilane
| Si(CH3)4
144
how can NMR help us identify a compound?
allows us to determine the amount of H and C environments in the molecule
145
what are the two types of NMR spectroscopy?
1H-NMR
| 13C-NMR
146
what are the aspects to look at in an NMR graph?
- number of peaks
- location of the peaks
- intensity of the signal
147
what are the two types of 1H-NMR spectroscopy?
high-resolution
| low-resolution
148
what is the difference between high-res and low-res 1H-NMR spectroscopic?
```
high-res:
- can see splits within the peaks
- can use the n+1 rule to determine neighbouring atoms
low-res:
- cannot see splitting
```
149
what information can be deducted from the number of peaks in a low-res 1H-NMR graph?
number of peaks = number of hydrogen environments
*beware of symmetry!!*
150
what information can be deducted from the location of the peaks in a low-res 1H-NMR graph?
location = degree of shielding
- closer to 0 = more shielded (upfield)
- further from 0 = less shielded (downfield)
151
what information can be deducted from the intensity of the signals in a low-res 1H-NMR graph?
intensity = number of protons in that environment
- area under peak is proportional to number of hydrogens
- height of peaks can be used as a ratio to calculate the number of each proton in each environment
152
what is the n+1 rule in NMR spectroscopy?
- ONLY in high res 1H-NMR
- n refers to the number of protons on the adjacent atoms
e. g. in CH3-CH2-OH
- the CH2 will split into a quartet because the adjacent atoms has three hydrogens
- the CH3 will split into a triplet
- but OH will only be a singlet as it is not attached to a carbon
153
what is the splitting ratio in a singlet?
no ratio, it is a single split
154
what is the splitting ratio in a doublet?
1:1
155
what is the splitting ratio in a triplet?
1:2:1
156
what is the splitting ratio in a quartet?
1:3:3:1
157
what information is obtained from 13C-NMR spectra?
indicate the number of different carbon environments by the number of different peaks observed
158
does height matter in a 13C-NMR spectra?
nope!
159
is there splitting in 13C-NMR spectra?
nopeee
160
what does the location of the peaks tell us in 13C-NMR spectra?
location = degree of shielding
161
what is infrared spectroscopy?
uses infrared radiation to excite the molecules of a compound and generates an infrared spectrum of the energy absorbed by a molecule
162
how can infrared spectroscopy be applied in real life?
- monitoring chemical pathways
- forensic examinations
- drug development
163
where is the fingerprint region in the infrared spectra?
<1500cm-1
164
what does the -OH functional group look like on an infrared spectra?
like a smooth tongue
165
what does the -NH2 (primary amine) functional group look like on an infrared spectra?
vampire fangs!
166
what does the -COOH (carb acid) functional group look like on an infrared spectra?
hairy beard
167
what are the advantages of NMR spectroscopy?
- highly sensitive
- small sample size
- sample can be solution
168
what are the advantages of mass spectroscopy?
- very sensitive
| - small sample size
169
what are the advantages of infrared spectroscopy?
- huge range of analytes and samples
| - small sample size
170
what are the advantages of UV-visible spectroscopy?
- useful for coloured organic and inorganic species
- simple to operate
- very cheap
- small sample size
- quick sample prep
171
what are the disadvantages of NMR spectroscopy?
- very expensive to buy
| - expensive to operate
172
what are the disadvantages of mass spectroscopy?
- very expensive to buy
| - expensive to operate
173
what are the disadvantages of infrared spectroscopy?
moderately expensive
174
what are the disadvantages of UV-visible spectroscopy?
not very sensitive
175
what are the four factors needed to be considered when designing a chemical synthesis process?
- availability of reagents
- reaction conditions
- yield and purity
- industrial uses
- environmental, social, and economic issues
176
what chemical synthesis process is most well known?
Haber's process
177
what is Haber's process?
the production of ammonia
| N2 + 3H2 ⇌ 2NH3
178
what reactants are part of the Haber's process?
```
hydrogen gas (H2)
nitrogen gas (N2)
```
179
how is hydrogen gas obtained for Haber's process?
hydrogen gas is derived from purified natural gas (CH4)
Ch4(g) + H2O(l) ⇌ 3H2(g) +CO(g)
180
how is nitrogen gas obtained for Haber's process?
- nitrogen gas is extracted from the atmosphere
- since air is ~78% nitrogen, it is readily available
- it is separated from O2 by cooling air down to ~-190˚C, where N2 is a liquid, while O2 becomes a gas
181
how does concentration affect the yield and purity of NH3 in Haber's process?
- when NH3 is produced, it is continually liquefied and removed
- applying LCP, the forward reaction will be favoured continuously, which will maximise both rate and yield of NH3
182
how does temperature affect the yield and purity of NH3 in Haber's process?
- process is exothermic (∆H=-92kJ/mol)
- lower temperature will cause the equilibrium to shift to the right towards the products side, favouring the formation of NH3
- however, low temperature will result in a lower rate of reaction
183
how does pressure affect the yield and purity of NH3 in Haber's process?
- higher pressure will result in the favouring of the reaction that produces fewer moles of gas
- the molar ratio of the reverse to forward reaction is 4:2, therefore, the forward reaction is favoured
- however, high pressures are expensive to maintain and can be extremely dangerous with pressure buildups
184
what are the reaction conditions required for the Haber's process?
- moderate temperatures (400-500˚C)
- moderate pressure (200-250 atm)
- addition of catalyst
185
how does change in temperature conditions affect the rate of reaction and yield of NH3 in Haber's process?
- high: ↑ rate of rxn, ↓ yield
| - low: ↑ yield, ↓ rate of rxn
186
how does change in pressure conditions affect the rate of reaction and yield of NH3 in Haber's process?
- high:↑ rate of rxn, ↑ yield
| - low: ↓ yield, ↓ rate of rxn
187
what catalyst is preferred in the Haber's process?
powdered magnetite
| *will NOT increase yield, only rate of reaction*
188
what are some industrial uses of NH3?
- fertilisers
- water purifier
- refrigerant gas
- pesticide
189
how is ammonia used in fertilisers?
- over 87% of ammonia produced is used in fertilisers
- it is a basic building block for ammonium nitrate fertiliser, which releases nitrogen, an essential nutrient for growing plants.
190
how is ammonia used in fertilisers?
used to prolong the effectiveness of chlorine added to drinking water
- boosts and prolongs the beneficial effects of chlorine, such as the improvement of taste.
191
how is ammonia used in fertilisers?
- natural refrigerant
- high thermal efficiency
- it works to capture and transfer heat energy to keep it separate from the cooling process
192
how is ammonia used in fertilisers?
- used to attract insects
- is combined with pheromones specific to the targeted insect
- the smell of the ammonia guides the insects to the insecticide
193
what is the environmental implication of the Haber's process?
- runoff from agriculture can end up in waterways
- leads to eutrophication
- algal blooms deprive the aquatic ecosystem of oxygen, causing deaths of flora and fauna
194
what is the social implication of the Haber's process?
- ammonia production industry provides jobs in both production and transportation
- large proportion of the world’s crop resources rely heavily on ammonia-based fertilisers
195
what is the economic implication of the Haber's process?
- constantly maintaining high temperatures and pressures in production is costly
- high reliance on electricity
- requirement of strong pipes and reaction chambers that are expensive to construct
