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

[pLuvia]

Next Question - explain the process of making ethene into polyethene?

Spoiler

Polyethylene can be produced via two ways, the Gas Phase process or the Ziegler Natta process (You don't need to know the second one)
For the gas phase process:
With high pressure (2600 atm) and high temperature along with a organic peroxide catalyst initator it forms a product with significant chain branching. Thus meaning at some carbon atoms one hydrogen atom is replaced by a alkyl group. This process yield LDPE
The Ziegler Natta process yields HDPE

More general:

The stages of production of polyethylene are:
Initiation: A chemical called the initiator starts the reaction by opening the double bonds of the ethylene which forms an ethylene free radical thus allowing other monomers to join onto it, as free radicals are very reactive.
Propragation: The monomers join to form a chain of monomers
Termination: When the free radical ethylene chain combine to form a complete polyethylene the process will stop

 

[UzurOger]

Well since there isn't a new question i thought i should put one up.

Q: Define Le Chatelier's Principle and identify factors that affect equilibrium in a reversible reaction.

 

[kazan]

when a system at equilibrium is disturbed, the system will adjust its self to minimize the changes

concentration
pressure
tempreature
volume



outline the history of the definition of acids and bases

 

[2006hsc]

outline the history of the definition of acids and bases

Lavoisor thought all acids contained oxygen. Proven wrong eventually.

Humphry Davy said that all acids contained replaceable hydrogen

Arrhenius said that all acids ionised in solution, creating hydrogen ions
- strong acids ionise completely
-weak acids ionise slightly

Bronsted-lowry came up with the theory that all acids were proton donors and all bases were proton acceptors

Next Question - how could you increase the validity in a acid-base titration?

 

[Petinga]

To increase the validity of a titration of acid- base repeat the experiment 4 times and average the titre. Do not include the first titre because this is often an estimation to determine the average titre.

Next Question: Describe the processes used to sanitise and purify the mass water supplies?

 

[2006hsc]

To increase the validity of a titration of acid- base repeat the experiment 4 times and average the titre. Do not include the first titre because this is often an estimation to determine the average titre.

isnt that reliability?

 

[kazan]

thats what i thought


whats the answer anyways
i dunno

 

[Riviet]

Increasing validity for a acid-base titration:

* Using the appropriate indicator for the titration, e.g using methyl orange indicator for a strong-acid and weak base titration

* Using the appropriate equipment for the procedure, e.g burette and pipette, although this point also helps to improve accuracy.

There's a couple more that I can't think of right now, anyone feel free to add.

Next Question:

Describe the process of refluxing and explain why is used. (3 marks)

 

[pLuvia]

Refluxing is used during esterification. Refluxing is the process of heating with a cooling condenser attached to prevent the loss of vapourised substancesthis allows for longer heating and so volatile substances do not escape during the experiment, which this can lead to inaccuracies in the measurements.
It also improves safety of the experiment as volatile components are flammable

Next question:

Name a branch in chemistry and explain the chemical principles used in it

 

[Sparcod]

Polymer chemistry?
This involves researching and designing and producing new polymers which can make the most out of current oil supplies or replace non-renewable resources.
Examples include: HDPE and trying to find ways to make it stronger and more resistant.

NEXT QUESTION:
Explain the usage of one radioisotope in industry or medicine.

 

[kazan]

cobalt 60

used in the medical industry

used to kill cancer

it decays to (mental blank here) which destroys cancerous cells

 

[onebytwo]

Polymer chemistry?
NEXT QUESTION:
Explain the usage of one radioisotope in industry or medicine.

industry radioisotope Am-241 is used in smoke detectors. it releases alpha particles and small quantities of gamma rays, however these are harmless as most of this is blocked by the outer casing. two electrodes have current passed through them thus ionising air particles and setting up an "equilibrium" (cant think of the right word), so when smoke is present the "equilibrium is disrupted causing the current to be minimised hence setting off the alarm. it has a long half life (?few hundred years?) meaning it doent need replacement. the main concern comes from its production at nuclear reactors. it is also very cheap to purchase on large quantities
EDIT: too slow..oh well...various answers are always useful...another q kazan...please

 

[kazan]

hmmmm


name the ester produced

octanol + butanoic acid

 

[pLuvia]

Octyl-butanoate.

Question
Using appropriate equations, explain the different combustion reactions that you have studied

 

[kazan]

complete combustion of ethanol

C2H5OH + O2 --> CO2 + H20 (not going to balance cuz u get the idea)

insufficient oxygen

C2H5OH + O2 --> CO + H2O

minimal oxygen

C2H5OH + O2 --> C + H2O


we can see, as the amount of oxygen decreases, the products formed differ,
this is not productive as C and CO, are pollutants, and lower the heat of combustion(is that right?)

with a plentiful supply of oxygen, we can see that combustion is at its prime, but the efficientcy of combustion is proportional to the amount of oxygen present.


a) find the molar heat of combustion,

when 220ml of water is heated, and it gains 10 degrees in temp, and the weight lost of the burner is 0.8g

b) find the molar heat of combustion if 50% of the heat was lost to the enviroment

 

[onebytwo]

er...dont we have to know what we're combusting to find the molar heat of combustion

 

[passion89]

er...dont we have to know what we're combusting to find the molar heat of combustion

Ethanol

 

[kazan]

er...dont we have to know what we're combusting to find the molar heat of combustion

whoops

it did say ethanol, but i must of edited it out sorry

 

[KYeh]

a) find the molar heat of combustion,

when 220ml of water is heated, and it gains 10 degrees in temp, and the weight lost of the burner is 0.8g

b) find the molar heat of combustion if 50% of the heat was lost to the enviroment

Before you read the solution please note:
- There are other ways of doing this problem
- A lot of my working out has been omitted to save time
- I make a lot of silly mistakes especially in calculations, so check it for me please ^_^ (found 3 mistakes just by rereading it, lol)

a)
1 Mol of ethanol = 46.068g

Therefore 0.8g of enthanol = 0.017 Moles

Using the formula E = mc(delta)T, the total amount of energy given off from 0.017Mol of ehtanol gives 91960J.

91960/0.017 = x/1 (cross multiplication where x = molar heat of combustion)

therefore x = 540911.76 J/Mol = 541KJ/Mol

b)
Since 50% is lost to air, therefore the amount used to heat the water is also 50% of the total heat produced, that means the total must be double the amount of heat put into the water,

2 x 540911.76 = 10818823.53 J/Mol = 1082 KJ/Mol

 

[GaganDeep]

Write an equation of water reacting with NaOH a B-L base.
I can't do it