Stopsign's Chemistry Marathon (2006) (1 Viewer)

[abbashussein]

this is a great revision forum

ok Question: Explain the procedure to test the emusifying action of a soap that you made 2 marks

 

[angmor]

set up two test tubes.
in test tube A, place 10ml of olive oil in 10ml of water
in test tube B, place 10ml of olive oil in 10ml of water, but add the soap.

observe the differences in mixing of both test tubes



QUESTION: use equations to show the effects of CFCs on ozone in the atmosphere

 

[Petinga]

Angmor that question has already been done on the previous page.


Describe the process by which ozone smog in cities occurs, including in your answer the origon of the pollutants, when the problem is at its worst and why.
The formation of phtotochemical smog involves ozone reacting with oxides of nitrogen with UV radiation. The pollutants such as oxides of nitrogen arise from combustion of fuels art high temps in vehicles and factories. This problem is at its worst in the afternoon when many workers are travelling home form work especially in large cities in the world such as sydney and Los Angeles.
Could someone expand on that for me coz i am unsure about this section

Explain the processes which produce acid rain inclusing in your answer the sources of the pollutants
Acid rain has a pH less than 5. It is caused by the high emissions of acidic oxides such as sulfur dioxide and oxides of nitrogen into the atmosphere. some sources of sulfur disoxide inculde burning of fossil fuels, volcanoe and extraction metals from oires. some sources of nitrogen dioxide are combustion at high temps and lightning strikes.
The sulfur disoxide and nitropgen oxides dissolve in rainwater forming weakly acidic solutions of sulfurous and nitrous acid. The sulfuruos acid and nitrous acid them undergo catalyutic oxidation to sulfuric and nitric acid. Thus acid rain is formed

In your course you performed an investigation to cpncentration of a domestic acid, describe the process that you undertook, did you results differ from what you expected, if so why?
This ivolved the use of titration in determing the concentrration of vinegar. This involved diluting a sample of vinegar by pippeting (i.e rinsed with water then vinegar) 25ml of vingar inhto a 250ml volumtetric flask(i.e clened with distilled water) with distilledwater being added to the graduation mark. A new pipette(rinsed with water then dilute vinegar) was then used to collect 25ml of diluted vinegar and placed in a conical flask(clened with distiulled water) with a few drops of phenolpthalein. 50ml of standardises sodium hyrdoxide was then added to a burette(rinsed with distilled water then NaOH). The knwon concentration of NaOH was then run into the conical falsk which was constantyl agitated. Once the equivalence point was reached, the tap was immediately closed on the burette. the volume of NaOH was recorded and titration was repeated four times for reliability. Using mole ratios the concentration of ethanoic acid in diluted sample of vinegar is determined then times by the dilution factor. Thus concentration of ethanoic acid is calculated.
The results were slightly out according to the value p;resented on the bottle of vinegar mainly due to inaccuracy of measuemenrts (i.e titres were rough), contamination and too much idicators added. However this could have been improved by using a pH meter allowing for exact equivalence point to be determined.

Why is it important to monitor cations and anions in our waterways
It is difficult to generalise saying cations and anions so i will explain 2 in detail like phosphates and lead.
It is important to monitor the concentration of cations in our waterways such as lead ions. Lead is an accumulative poison that builds up in the body causing mental deterirotation and eventual death. This can be monitoted using Atomic Absobrtion Spetrsocpy. It is also quite important to monitor the concentration of anions in our waterways such as Phosphates which lead to excess algal blooms and hence eutrophication. this is cuased by diuscharge of phospahetes from fertilliers and washing detergent into inland lakes and rivers leading to a reduction of oxygen due to algae preventing atmospheric oxygen and light from penetratiogn water and hence leads tro death of many aquatic species.this must be kept between 0.01 and 0.1 ppm to prevent drastic effects on environemtns. Thus shows importnace of monitoring of phosphates and lead ions in society and enviuronment.

Question: Describe some techniques used to monitor ozone concetrrations in atmosphere and genral trends of ozone concentration

 

[Naylyn]

It is vital the you include equations.

If there is an equation that can be included you will not get full marks unless you do, a detailed explaination is not enough, if are not sure that the equation is right write it in the margin that way you shouldn't lose marks if it is wrong.

Question: Describe the process by which ozone smog in cities occurs, including in your answer the origon of the pollutants, when the problem is at its worst and why. (Should have been photochemical smog, my bad)

Ozone forms in the lower atmosphere on days of high intensity sunlight such as those on hot summer days, when concentrations of NO2 are well above clean air levels.

The sunlight splits an oxygen atom from NO2 which then reacts with O2 to form ozone

NO2 + sunlight --> NO + O
O + O2 --> O3

NO can destroy ozone;

NO + O3 --> NO2 + O2

So the photochemical smog is at its worst when there is much more NO2 then NO, meaning that the NO cannot destroy the ozone fast enough.

There are many reactions that transfrom NO into NO2 including;
NO + O2 + carbon dioxide + sunlight --> NO2
2NO + O2 --> 2NO2

As the day goes on the ratio of NO2 to NO increases meaning that the concentration on O3 increases until by about 2 o' clock the probelm it at its worst, then the decreasing intensity of the sunlight reduces the production of ozone.

Cars are the main source of NO2 and NO in cities.

 

[Petinga]

Naylyn i know all those equations for da questions i have posted up but dnt like typing them out. dont worry i would have da top postion in my school if i didnt know all da equations coz my teacher expects them for all questions

yea could someone explain the formation of phtochemical smog for me

 

[Naylyn]

It's there now^^. Post up some new quesitons please.

Question: Contrast the processes that produce low-density polyethylene and high density polyethylene.

 

[pLuvia]

LDPE are produced by the gas phase process whereby the polyethylene is produced by high pressures and high temperatures along with an initator, organic peroxide, which forms a product with significant chain branching and has a low density.

HDPE are produced by the Ziegler Natta Process, with pressure of a few times of atmospheric pressure and temperatures of 60 degrees and a catalyst of titanium (III) chloride and a trialkylaluminium compind forms an unbranched polyethylene molecule which can pack closely together and has a high density.

Describe the uses of polyvinylchloride and polystyrene with reference to their properties

 

[Petinga]

Polyvinylchloride(PVC) is normally brittle and uv sensitive. However in the abscenece of uv light it is rigid allowing it to be used in underground water and sewage pipes. However with additives, PVC, becomes water and chemical resistant allowing it to be used in garden hoses and rigid guttering and piping.

Polystyrene is transparent due to very feww crytals in its strucutre. This gives it uses in transparent pipes and sheets as well as compact disk covers. It is also rigid due to the prescence of the benzene ring which gives it usese in tool handles, buckets and plastic funrniture. However with additives such as gas it form a foam giving it uses such as home insulation, floats and pakaging.

Question: discuss the need for alternative for the petrochemical industry

Question: Identify a variety of chemical occupations and role

Question: Describe the process by which ethene is obtained form crude oil

 

[Naylyn]

Polyvinyl chloride has excelent electrical insulation properites and is generally very tough and flexible, however it is not weather resistant and as such should not be exposed to direct sunlight. These properties make it perfect for use in electrical insulation in the home.

Polystyrene is an excelent insulator of heat and when it is made in foam form it is a very effective low density insulator. It is used in foam drinking cups and insulation because of its insulation properties.

 

[Naylyn]

Question: discuss the need for alternative for the petrochemical industry

The petrochemical has a variety of social and environmental problems asociated with it, the main ones being;
-The petrolium of the world is not infinite and will run out in the next 30 years according to many.
-When the products of petrolium are burned they release CO2 which is considered by the vast majority of the worlds governments and leading scientists to be the cause of global warming.

Because of these vast problems a alternative source of the products that are now produced by the petrochemical industry is need, however this is a problem since the alternative source must be able to produce the huge quantity of product that the petrochemical industry produces without adding to the greenhouse effect.

Question: Identify a variety of chemical occupations and role
-Lab Assistant: Produces the variety of solutions and chemical that the chemists in the lab require for their experiments, must be familiar with range of chemicals and chemical procedures
-Salvage Chemist: Salvages artefacts from a variety of places, including shipwrecks and ancient ruins, must be able to restore the various irreplaceable artefacts without error and must be familiar with the techniques used to salvage a variety of materials including iron, silver, copper, wood, leather and glass.
-Pyrotechnician: Prepares explosives that are required for a variety of inductries including the mining industry and the special effects industry, must be able to safely prepare highly dangerous chemicals.

Question: Describe the process by which ethene is obtained form crude oil
Ethene is produced by the process of cracking the less valuble products that are produced from crude oil by fractional distillation. There are two primary types of cracking, thermal cracking which invloves high temperatures and preassures and catalytic cracking which uses relatively low temperatures and presaaures and an aluminium zeolyte catalyst.

The cracking of ethane is as follows
C2H6(g) --> C2H4(g) + H2(g)

Question: contrast addition and condensation polymerisation

Question: how are transuranic elements produced

Question: name a radioactive isotope that is used in industry and explain why that isotope is ideal for that purpose

 

[Petinga]

Question: contrast addition and condensation polymerisation
An addition polymer is formed when alkene monomers such as ethene, combine via addition reactions to produce long chained polymers of high molar mass such as polyethylene, with no other products.

......+[C2H4]n +.... ->[C2H6]n​

A condensation polymer is formed when two different polymers combine to produce polymer with the elimination of a water molecule.​

............+ [C6H12O6]n + ...... -> [C6H10O5]n + H2O​

Question: how are transuranic elements produced
Transuranic elements have an atmoic number greater than uranium. These can be produced either in particle accelerator or nuclear fission reactor.
In high speed particle accelerator, the nucleii of heavy elements are bombarded by high speed positive particles such as H, He, B or C.
In nuclear fission reactor, the nucleii of heavy elemtns are bombarded by neutrons. e.g. neptunium produced by the bombardment of U-238 witht neutrons

Question: name a radioactive isotope that is used in industry and explain why that isotope is ideal for that purpose
Cobalt-60 is used in industrial radiography to inspect metal parts for welds and defects such as hairline cracks, metal fatigue and poor welds.
some propereties related to its use are:
-long half life of 5.37 years minisimising need for replacement and maintenance hence reducing exposuire of radiation
-higly penatritive gamma ray emmitter that allows detection of flawas in metals parts far underground ground
-can be used in a chemically inert form inside a sealed container hence reducing radiation exposure

Questions:
1. Name a radioactive isotope that is used in medicine and explain why that isotope is ideal for that purpose
2. Describe some processes and techniques used to detect ionising radiation
3. Describe a named Biopolymer and its potential


​

 

[Naylyn]

1. Name a radioactive isotope that is used in medicine and explain why that isotope is ideal for that purpose
Technetium 99m is widely used in medical diagnosis. A blood serum containing technetium 99m is unjected into the body and collects in blood clots and other places where the blood flow is restricted, radiation measurement devices can then be used to detect these problems. It is ideal for this purpose since it has a short half-life of about 6 hours and emits low intensity radiation meaning that it causes little or no damage to the paitent.

2. Describe some processes and techniques used to detect ionising radiation
Geiger-Muller counter-
-contains a chamber with an inert gas (usually argon) with a potential difference across it.
-radiation enters through a hole in the chamber, when it hits an argon atom it strips it of some of its electrons.
-the electrons head towards the positive electrode gaining speed and ionising more argon atoms as they go, the positive argon atoms head towards the negative electrode
-this shows up as an electric pulse which is amplified and displayed in the form of an pulse.

3. Describe a named Biopolymer and its potential
One polymer that is currently being used is the polymer plantic. Plantic is made from corn starch and is 100% biodegradeable. Apart from it biodegradeability it's properites are almost exactly the same as the plastics that are currently being used to package food products meaning that it has the potential to prevent a large amount of rubbish going into landfill each year.
​

Question:describe the layered structure of the atmosphere

Question:what are the main factors to be considered when determing the quality of a water sample

Question:describe the differences between the alkanoic acid and alkanol functional group

 

[Petinga]

Question:describe the layered structure of the atmosphere
The earths atmosphere is composed of a layered structure with a mixture of gases. The first layer, the troposphere, extends from earths surface to 15km above sea level. It is composed of mainly nitrogen, oxygen, carbon dioxide, argon and water vapour. Asw altitude increase temps decrease from 25 degree to minus 25 degrees. The next layer, the stratopshere, extends form 15km-50km above earths sea level. it is composed of mainly nitrogen,ozone and oxygen. as altidue increase, temps increase from - 25 degrees to 25 degress. THe next layer, the ionsphere comprises thje mesopher and thermosphere. the mesophere extends from 50 to 85 km above eaths sea level. as altituide increases, temps decrease form 25 degress to -100 degress. the thermosphere extends from 85 to 120km above earths sea leavel. as altitude increase, temprs increase form -100 to 25 degree. both are compose of No, O and o2.
Question:what are the main factors to be considered when determing the quality of a water sample
the main factors that need to be considered are :
-common anions and cations
-turbidity
-total dissolved solids
-acidity
-dissolved oxygen
-biochemcial oxygen demand
-microrganisms
-hardness
Question:describe the differences between the alkanoic acid and alkanol functional group
Alkanoic acids have the funtional -COOH group (carboxylate group) and alkanols have a functional -OH group (hydroxy group). Alkanols have genra; formula CnH2n+1OH and alkanoic acids R-COOH with R being alkyl group.

Questions:
1. name some pollutants in lower atmosphere
2. differentiate between coordainte covalent bond and coordinate covelent bond
3. Describe some qualititav and quanitiave tests carried out in yopu course of chemistry on water sample
4.Describe the signifcane of Haber process on Germany during world war1
5. How would you distingiush between wheter copper, iron or lead ions were presente within a particlar sample of water
6. Discuss cellulose potewntial to replace petroleum in petrochemical industry

 

[Naylyn]

1. name some pollutants in lower atmosphere
Some common pollutants in the lower atmosphere are Nitrous Oxide, Nitrogen Dioxide, Nitrogen oxide, ozone and peroxyacetly nitrates.

2. differentiate between coordainte covalent bond and coordinate covelent bond
A covalent bond is a bond in which each atom shares electrons that both atoms donated to the bond. In a coordinate covalent bond both atoms share electrons in a bond but the electons both come from the same atom.

3. Describe some qualititav and quanitiave tests carried out in yopu course of chemistry on water sample
Determing the total dissolved solids:
-Obtained a water sample from a local waterway
-Measure a 100mL sample of the water
-Filter the water in eliminate the undissolved solids
-Measure the weight of an evapurating basin
-evapourate the water in the basin
-weigh the basin and the residue to find the total dissolved solids
we didn't actually do this experiment what do you think plausible resulits would be?

4.Describe the signifcane of Haber process on Germany during world war1
The development of the Haber process gave the German farmers independance from the imported salt petre from south america, also the ammonia produced could be used in the manufacturing of weapond accellerating the nation towards the war
5. How would you distingiush between wheter copper, iron or lead ions were presente within a particlar sample of water
Either of these test will be sufficient
Add NaOH which will form a blue precipitate if copper is present.
Add a substance containing Cl^(-) if lead is present a yellow precipitate will form, then add F^(-) if a white precipitae forms lead is present.
6. Discuss cellulose potewntial to replace petroleum in petrochemical industry
Cellulose contain 4 carbon atoms linked in a straight line which means that it could be considered as a starting point for the creation of ethene, pentene and butene. The limitations of this are the fact that there is no efficient way to break cellolose into it's monomer glucose.

Questions
1. Describe the naming of esters and relate it to the reactants that produced it
2. What indicators would be used in a strong acid weak base titration
3. Explain what is meant by strong and weak acids in terms of ionisation
4. What is the use of acids as food additives
5. Define Le Chateliers principle

 

[little master]

answers to post by petinga
1.)
-CO- cars cigarettes, bush fires
-SO2-combustion of fossil fuels form motor vechiles, powerplants, Metal sulfide smelters
-Oxides of NO- combustion of fuels, burning of biomass
-Pb- Leaded fuels, disposing of leaded batteries
Particulates- Incomplete combustion

2)
Covalent BOnd: between two atoms is when each pair of atoms provides 1 pair of electron to the pair
Co-ordinate Covalent: Both electrons are provided by one atom called the donor atom

6.)
The long chain carbon structure of cellulose gives it potential to replace crude oil as the source of petrochemicals.The conversion of long chain cellulose to glucose monomers, by acid hydrolysis or by enzymes is currently possible but not economically viable.
Biomass fuels cost more than fossil fuels due to the complicated conversion process, its advanteges are negated if the energy required to plant, tend and convert the biomass is derived from fossil fuels, arable land must be used to grow dedicated fast- growing crops, creating deforestation of the natural environment.

 

[little master]

haha a bit slower

 

[Naylyn]

Post some questions please, everyone.

 

[bboyelement]

how is ozone monitored in the atmosphere?

 

[little master]

this was in last year paper. i didnt completely understand it . just hv a vague idea on this

The flow chart shows a series of steps involved in the production of ethyl butanoate.
glucose--->mixture containing ethanol--->pure ethanol--->ethyl butanoate

Describe the chemistry and procedure involved in each of these steps.

 

[little master]

damn slow again!!!