Chemical Monitoring and Management Flashcards
what do forensic chesmists do?
A forensic chemist anylses samples from a crime scene, such as bomb fragments, residues of chemicals, glass, hair samples, paper and blood stains, as part of the larger process in solving a crime. much of the work of a forensic chemist is down to accurately detecting minute traces of chemical evidence which could be used in the court of law.
what skills must a forensic chemist have?
a forensic chemist must be intelligble in the following scientific areas :
- geology
- biology
- genetics
- soil chemistry
- material science
what instruments might a forensic chemist use in the field?
- miroscopy
- UV, IR and Xray anaylsis
- gas chromotography and mass spectroscopy
these instruments make the work of a forensic chemist faster and more efficient.
what is the name of the chemical principle and technique that the forensic chemist uses?
Gel Electrophoresis which is an analytical technique, relying on the principle that biological molecules have an electric charge
how does gel electrophoresis work?
electrophoresis involves the seperation of chemicals along a solid medium in the presence of an applied potential difference. the solid medium is often a polyacrylamide gel. the appartus consists of a gel slab, electrolyte solution, power source, an anode and cathode and a cloth wick.
whats the equipment involved in Gel electrophoresis?
the solid medium is often a polyacrylamide gel. the appartus consists of a gel slab, electrolyte solution, power source, an anode and cathode and a cloth wick.
how does electrophoresis work?
protein samples called from traces of blood at a crime scene can be hydrolysed into a mixture of amino acids. these amino acids are then loaded into wells in the porous gel. a current and different buffers are applied. the smaller and more charged the amino acid is, the further it will move. eventually, based on their migration rates, the amino acids become separated and made visible once sprayed with ninhydrin to make them visible and identified.
what is gel electrophoresis used for in forensics?
used to detect and compare proteins in blood from an unknown source, helping the forensic chemisty in making clear connnections and narrowing down the case.
what is collaboration?
the sharing of findings, information and research methods between scientisists in different sub disciplines
why is collaboration important?
- collaboration reduces the work load for chemists, thus relieving stress and thus increasing efficiency. this reduces the time taken to complete a given project and reduces cost
- the communication of ideas to share knowledge allows for the advancment of research and personal growth and collective chemists can bounce ideas off eachother and learn new skills and develop more as a person
- different chemists specialise in different fields and hence some problems are better soled with the assistance of specialist chemists. Also, most real world problems occuring today require a broad range of chemical knowledge which only a selectiv few specialise in
- reliablity and validity are strengthened by peer crtiquing
what is an example of a chemical reaction which needs monitoring?
combustion of petrol
why does the combustion of petrol need monitoring?
the combustion of petrol results in the formation of different products depending on the conditions involved. some of these products are powerful pollutants such as carbon dioxide and soot
what happens when oxygen is in plentiful supply in combustion?
complete combustion occurs! this means that the byproducts of the reaction are water and carbon dioxide
why is complete combustion often unlikely in regards to the combustion of petrol?
assuming octane is petrol, for every one mole of petrol that is burnt, an incredible 12.5 mol of oxygen is required for complete combustion. often in small and confined systems, such as in the engines of cars, complete combustion rarely occurs due to this large oxygen supply
what are the usual products of incomplete combustion?
soot, carbon dioxide and/or carbon monoxide
why is carbon monoxide bad?
-disrupts the human bodys ability to transport oxygen by displacing oxygen in the blood by affecting haemoglobin molecules. this deprives the heart, brain and other vital organs of oxygen
why is soot bad?
- when breathed in can cause respiratory conditions such as coronary heart disease, ashma, bronchitis and even cancer.
- soot build up in car engines can cause more engine wear and tear
at high temperatures, what else do combustion reactions form and why are these products bad?
nitrogen gas and oxygen gas can react to form the famous nitrous oxides such as nitrogen dioxide and nitrogen monoxide
these oxides not only can cause acid rain but, in particular nitrogen dioxide, can produce photochemical smog, leaving ozone, which is a powerful lung irritant and oxidising agent even in small conentations which is extremely toxic to humans
because petrol contains impurities, what else can be indirectly formed in combustion reactions and why are these products bad?
sulfur impurities in petrol can react with oxygen gas in the air at high temp and form sulfur dioxide. sulfur dioxide can cause a multitude of respiratory conditions such as bronchitis and can form acid rain
carbon dioxide is often released as a by product during combustion. why isnt it as bad as a pollutant than other combustion pollutants?
carbon dioxide can be harmful, but it is mostly absorbed into the environment
what are some chemist faculties?
- analytical chemistry
- Nuclear Chemistry
- Industrial chemistry
- forensic chemistry
what is ammonia used to make?
- cleaning products on both an industrial and domestic level
- Fertilisers such as ammonium phosphate, sulfate and nitrate
- Nitric acid
why is ammonia used to make cleaning products?
acqueous ammonia solution is used as a cleaning agent because of its basic nature, allowing it to emulsify grease stains and other unwanted marks.
it also leaves no residue behind because the water and ammonia in the solution evaporates into the air
why is ammonia used to make fertilisers?
ammonia is a source of fixed nitrogen, an element which is essential in the growth of plants
why are fertilisers and thus ammonia important?
fertilisers are used to satisfy the demands of farmers growing food crops
how are most fertilisers made?
by reacting ammonia with some common acids including HNO3, H2SO4, and H3PO4
how is ammonia made to produce nitric acid?
through the oswald process
what can be made with nitric acid?
- fertilisers
- can produce gunpowder and explosives
why are nitrogen compounds used to make explosives? give examples
some nitrogen compounds or mixtures have the ability to decompose suddenly and produce large volumes of gas at extreme pressure, making them the perfect explosive
examples include TNT (trinitrotoluene), gunpowder (potassium nitrate) and dynamite (nitroglycerin)
what is the haber process?
the industrial process used to make ammonia from its constituent gases nitrogen and hydrogen
what are some characteristics of the haber process reaction?
- its reversible (le chateliers principle oh boy!)
- its exothermic
- involves the elements nitrogen and hydrogen
- proceeds very slowly at atmospheric temp and pressure
how can nitrogen be obtained for the haber process?
- via fractional distillation of liquefied air
- when methane reacts with air over a nickel catalyst to remove oxygen, which would form an explosive mixture with hydrogen if it were allowed to remain. in the process, hydrogen and nitrogen are formed
2CH4(g) + O2(g) + 4N2(g) –> 2CO(g) + 4H2(g) + 4N2(g)
how can hydrogen be obtained for the haber process?
- most common method is the hydrolysis of water, seperating the constituents oxygen and hydrogen. except where electricity is plentiful and inexpensive, hydrogen is not obtained in this way
- hydrogen can be made inexpensively by re-forming light petroleum fractions or natural gas by reacting it with steam
- carbon monoxide can be converted into carbon dioxide in a reaction resulting in more hydrogen
for every mole of ammonia produced,…
46kJ of energy is released
why is the rate of reaction increased with higher temperatures?
as temp increases within a system, the particles in that system gain more and more kinetic energy, beginning to move more frequently and eradicably. this increases the frequency of collisions between these particles, breaking their intramolecular bonds in the process.
therefore, there is more of a likelihood for successful collisions , collisions which must satisfy correct speeds and orientations, increasing the rate of reaction in accordance with collision theory
what happens to the yield of ammonia in the haber process at high temperatures and why does this occur?
the yield of ammonia is reduced because the reaction is exothermic (it releases heat). therefore when temp is increased, effectively their becomes an excess amount of heat which the system begins to reduce by shifting to favour the reactants, hence ammonia product is reduced
well, if high temps means less product but faster reaction rates, what does this mean for the hater process reaction?
compromise conditions of 450 degrees must be established to strike the perfect balance between efficiency and amount of ammonia
what is the equilibrium like at atmospheric temperature and pressure in the haver process?
the reaction proceeds very slowly and the equilibrium lies very much to the left favouring the reactants. in theres conditions, the triple bond in nitrogen and the single bond in hydrogen are reasonably strong and resist breaking to make ammonia
what does a catalyst to in the haber process?
a catalyst used in the haver process has no effect on the equilibrium position, but only provides an alternative reaction pathway that has a lower activation energy, and, in turn, increasing the rate of reaction
allows the nitrogen and hydrogen bonds to be more easily broken
why is using a catalyst in the haber process advantageous?
because using a catalyst permits the process to be operated at lower temperatures, temperatures which previously fostered a slow reaction rate in accordance with the collision theory but favours the forward reaction and thus produces a high yield of Ammonia
low operating temperatures reduce the cost of production, improving economic viability
whats the common catalyst used in the haber process and why?
it is common for magnetite iron oxide to be used as the catalyst. this is because the substance is highly porous and provides a large surface area for the reaction to take place
what other compounds can be added to the catalyst and why?
minor components called promoters such as calcium and aluminium oxides may also be added to support the structure of the catalyst and maintains its high surface area
potassium can increase the electron density of the catalyst, thereby improving its reactivity
what happens in the haber process when pressure increases?
when the pressure of the equilibrium increases, the equilibrium will shift in the forward direction according to Le Chateliers principle. hence the forward reaction is favoured and a higher yield of ammonia is produced
why is the forward reaction favoured when pressure in the haver process is increased?
in the haber process, for every 4 moles of gas which reacts, two moles of product is produced.
increasing the pressure forces the reaction mixture into a smaller volume, pushing each molecule closer together and increasing their chance of colliding and sticking to the catalysed used. via the collision theory, this increases the reaction rate
so, does increasing pressure in the haber process have a small or large impact?
a significantly large impact
what other concerns arise from the use of high pressure in the haber process?
- operating at higher pressures increases the rick of an accident as equipment is placed under extreme strain. this means that extremely strong, reinforced pipes and containment vessels must be made to withstand these pressures. this increases the production costs
- high pressures cost a lot to produce and maintain. therefore, running costs are very high
- monitoring and maintaining high pressure increases job opportunities for society which is good
- occupational safety issues need to be considered
what are the compromise conditions of the haber process?
temperature: 450 degrees Celsius
pressure: 250 atmospheres
in the end, what is the main and absolute goal for the haber process?
to make a profit.
why is monitoring in the haber process CRUCIAL?
producing ammonia in this process is an around the clock process. all components of the process must be monitored and managed for the effective and optimal production of ammonia. monitoring also ensures safety and efficiency
what list of things need to be monitored in the haber process?
- temp and pressure
- the feedstock nitrogen and hydrogen gas
- the presence of contaminants
- movement of the products through the reaction vessels
- the structural integrity of the reaction vessels
why are compromise conditions needed in the haber process?
to strike the perfect balance between effectiveness, safety and cost
describe the monitoring required for temp and pressure in the haber process?
-temp and pressure must be maintained within acceptable limits for optimal production of ammonia.
but, too high a temp can damage the catalyst and damage other components of the reaction vessel.
the pressure of the reaction vessel should also be maintained at a high level to promote a high level of ammonia production. but to high a pressure may cause the containing vessels to rupture, proving to be a major safety hazard.
maintaining high temp and pressure is also costly
describe the monitoring of the feedstock mixture of nitrogen and hydrogen gas fed into the reaction chamber?
the nitrogen and hydrogen that is fed into the containing vessels must be in a stoichemetric ratio of N:H 3:1, and must be pure and free of contaminants
the ratio should be maintained in this way to ensure no build up of any one reactant, thereby decreasing optimum efficiency
what contaminants can enter the reaction vessel in the haber process and what are their effects?
- oxygen, can react with flammable hydrogen and or nitrogen to produce a very damaging explosion
- argon(and any other noble gas), lowers the efficiency of the ammonia production
- sulfur compounds, can damage the expensive catalyst
- carbon dioxide, can damage the expensive catalyst
- methane, lowers the efficiency of the process and risks explosion
describe the monitoring involved in the movement of materials in the process
products must also be monitored to ensure they are continually condensed and removal from the reaction vessel so as to drive the equilibrium forward. this must be done at regular intervals and must be monitored to ensure no impurities contaminate the product
unreacted gases must also be fed back into the reacting vessel an recycled
describe the monitoring involved in the structural integrity of the equipment in the haber process?
the structural integrity of the reaction vessel and seals must be maintained to ensure safety and proper functioning of equipment
in what significant period did haber fabricate his ingenious process of ammonia production?
during the first world war
why was something like the haber process required during the first world war?
agriculture and industry were competing for the dwindling supplies of nitrogenous materials. Peruvian guano was exhausted by 1900 and sodium nitrate from Chile was also coming to an end.
as well as the above, an allied embargo strangled germanys overseas supply of raw materials from the rest of the world. this stopped Germany importing nitrates from Chile for use in agriculture and as well as in the manufacture of gunpowder and explosives
German industry therefore needed to be able to meet the country requirements for fertilisers and the tremendous demands for explosives
how significant was the haber process in its time of world history?
the haber process was very significant, allowing Germany to stay clinger to the war effort, without it the war effort could not have been sustained for long as food could not have been produced at a rate to feed the population
despite many labelling him as a war criminal, his contribution to the war effort was so significant that Haber was awarded the Nobel prize in chemistry in 1918.
haber also improved the nutrition of humanity by providing the world with a reliable source of synthetic fertilisers
whats the first test performed to identify cations in a sample?
adding HCl until a precipitate forms
after adding HCl, what is the precipitate and what colour is it?
the precipitate is white and it is lead chloride
after the first test for cations, what do you do next?
filter the sample and add H2SO4 until a precipitate forms
whats the issue when you add H2SO4 to a sample and a precipitate forms?
the precipitate could be one of two things, calcium sulphate or barium sulphate
what tests can be done to distinguish between barium sulphate and calcium sulphate?
flame tests
or
adding sodium fluoride, if a precipitate indicates calcium and no precipitate indicate barium
after adding H2SO4, whats the next test?
filter the sample and add sodium hydroxide
whats the issue with adding sodium hydroxide and a precipitate forms?
the precipitate could be one of two things, iron(II) hydroxide or iron (iii) hydroxide
what test can be done to distinguish between the two iron hydroxides?
add KSCN, potassium thiocyanate
if a red solution forms, iron(III) is present
if a clear solution forms, iron(II) is present
if a precipitate doesn’t form when sodium hydroxide is added, what else does it indicate?
a blue solution forming indicates the presence of copper (II)
ammonia can be added to confirm that the colour is blue
what is the flame colour for barium?
light green
what is the flame colour for calcium?
brick red
what is the flame colour for lead?
blue-tinged white
what is the flame colour for copper?
blue green
what is the flame colour for iron?
yellow
in testing for any ion, why must you test in order using a flowchart etc?
ensures that there is no other ions present which can intefere with the one you are trying to find. for instance, in testing for calcium, you must first test for lead or else the precipitate formed could be lead sulphate instead of calcium sulphate. this is why you add HCl first to precipitate out the lead as lead chloride
what is the first test in identifying anions in a sample and what are the results?
add HNO3
if efference is observed, carbonate ion is present
what next after adding nitric acid to test for cations and what are the results?
add barium nitrate
precipitate indicates the presence of sulphate as barium sulphate precipitates out
