Hsc Marathon 2009 - Chemistry (1 Viewer)

[aero135]

You may have seen similar threads in other forums. In past years students have found it a great way to quiz each other on various areas of the syllabus and share their knowledge in preparation for the HSC Exams so I thought I would start one for the 2009 Chemistry students.

How To Play
The first person asks a Chemistry question (preferably from the core topics as everyone does these). The next person answers it then posts another question for the next person then so on.


Tip:
If you feel an area is your weakness then try asking a question on this area to see others responses to it which may help you in your understanding.

First question: What is a galvanic cell? Describe its set up

 

[Timothy.Siu]

umm galvanic cell?
it is that thing wheres theres 2 things with electrodes and electrolytes lol, and it makes an electric current or something lol.
they have like salt bridges joining those 2 things
someone else can answer that one

but yeah i'll ask a question,
why is ethylene more highly reactive?

 

[kaz1]

umm galvanic cell?
it is that thing wheres theres 2 things with electrodes and electrolytes lol, and it makes an electric current or something lol.
they have like salt bridges joining those 2 things
someone else can answer that one

but yeah i'll ask a question,
why is ethylene more highly reactive?

Ethylene is highly reactive due to the presence of the C=C double bond.

Outline why Ethanol is a renewable resource.

 

[shady145]

^ because we can produce ethanol using simple sugars found in plants. we can then grow the same plant over and over making it a renewable source.

how are transuranic elements produced?

 

[aero135]

Transuranic elements are elements with an atomic number greater than uranium. They are produced in either nuclear reactors or particle accelerators. Nuclear reactors produce neutron efficent isotopes by spliting a uranium atom to gain neutrons. Then firing these neutrons at an element

For e.g. cobalt 60

Particle accelerators accelerate particles using a magnetic field. Nuclei of atoms can be accelerated and bombarded with a target. This is how Hassium is produced by bombarding lead ions with and iron target.

Next Question : Explain the displacement of metals in the reactivity series.

 

[Kaatie]

The activity series lists metals in order of decreasing activity. The series can be used to predict whether displacement reactions will occur between a metal and a metal ion in solution. As a rule a displacement reaction will occur spontaneously if the metal is more active than the metal that is present as ions in the solution.

define fractional distillation

 

[lyounamu]

The activity series lists metals in order of decreasing activity. The series can be used to predict whether displacement reactions will occur between a metal and a metal ion in solution. As a rule a displacement reaction will occur spontaneously if the metal is more active than the metal that is present as ions in the solution.

define fractional distillation

Fractional distillation is a distillation to separate volatile chemical substances in which the products are collected in a series of separate fractions, each with a higher boiling point than the previous fraction.<!--//
//--><!--EOF_DEF-->

What are isotopes?

 

[bored of sc]

Displacement of metals: a more reactive metal will replace a less reactive metal in it's compound i.e. x(s) + yz(aq) --> y(s) + xz(aq). In this case x is more reactive than y.
Reactivity series: The many combinations of these displacement reactions allow for an electrochemical series to be generated --- this series lists the metals in order of reactivity. A metal will undergo a displacement reaction if it is higher in the series than the metal (in the solution) with which it is reacting.



Outline the three steps involved in an addition polymerisation reaction. (3 marks)

 

[Kaatie]

isotopes are atoms of the same element that have the same atomic number but different mass number, they have the same number of protons but different number of neutrons

What is the main source of ethylene

 

[bored of sc]

Fractional distillation is a distillation to separate volatile chemical substances in which the products are collected in a series of separate fractions, each with a higher boiling point than the previous fraction.<!--//
//--><!--EOF_DEF-->

What are isotopes?

Haha. I was too slow for the metal reactivity question.

An isotope is an element with an increased or decreased number of neutrons in the nucleus.

 

[Kaatie]

oh i feel so bad doing that to you twice lol

 

[bored of sc]

isotopes are atoms of the same element that have the same atomic number but different mass number, they have the same number of protons but different number of neutrons

What is the main source of ethylene

Oh man, beaten again.

The main source of ethylene is petroleum. It is separated into fractions through fractional distillation. Following this longer-chained hydrocarbons are broken down into smaller-chained, more economically viable hydrocarbons including ethene in process called catalytic cracking.

 

[bored of sc]

Outline the three steps involved in an addition polymerisation reaction. (3 marks)

 

[Kaatie]

you forgot to ask a question

 

[Kaatie]

oh now i got beaten as you did ask a question lol.

1. The reactive double bonds between two of the monomers break
2. Two monomers join to produce a reactive dimer
3. This process is continued and builds up a chain

describe the process of cracking

 

[bored of sc]

oh now i got beaten as you did ask a question lol.

1. The reactive double bonds between two of the monomers break
2. Two monomers join to produce a reactive dimer
3. This process is continued and builds up a chain

You got it correct but I suggest using the key words of initiation, propagation and termination.

1. Initiation: the reactive double bonds from the monomers break with the help of a catalyst, forming free radicals (unpaired electrons) which are highly active.
2. Propagation: the free radicals pair up/bond with neighbouring monomers to produce a chain of monomers.
3. Termination: the process stops producing a polymer.

I'd still give you 3/3; what I have above is just a little bit extra.

By the way, dimer is an excellent scientific term.

 

[bored of sc]

describe the process of cracking

I'm rusty on this dot-point.

Cracking is a process of chemical decomposition whereby longer alkanes are broken down into shorter hydrocarbons (usually alkanes and alkenes). This process is used in the industrial production of ethylene. Catalytic cracking makes use of a catalyst such as zeolite (aluminium silicates) to lower the activation energy required to break up the bonds in the long-chained hydrocarbon. Thermal cracking occurs at very high temperatures and pressures e.g. 500^oC+ to break the relatively strong C-C bonds.

I.e. catalytic cracking: longer alkane --> (catalyst) alkane + alkene
e.g. C₃H₈ --> (zeolite cat.) CH₄ + C₂H₄

 

[bored of sc]

What properties would you consider to be neccessary in a radioisotope used:
(i) in a thickness gauge
(ii) for detecting leaks in a water pipe
(iii) for irradiating (and destroying) cancerous cells in patients
(iv) for sterilising medical supplies
(v) for diagnosing blood-circulation problems in the ill
(vi) in a smoke detector
(vii) for internal irradiation of tumours in the thyroids gland ?


Properties include type of radiation emitted, half-life, physical properties of element e.g. water soluble, chemical properties e.g. ability to combine with bodily substances etc.

 

[scora]

taking a stab-

What properties would you consider to be neccessary in a radioisotope used:
(i) in a thickness gauge
(ii) for detecting leaks in a water pipe
(iii) for irradiating (and destroying) cancerous cells in patients
(iv) for sterilising medical supplies
(v) for diagnosing blood-circulation problems in the ill
(vi) in a smoke detector
(vii) for internal irradiation of tumours in the thyroids gland ?


Properties include type of radiation emitted, half-life, physical properties of element e.g. water soluble, chemical properties e.g. ability to combine with bodily substances etc.

(i)gamma emitter
(ii)water soluble. gamma emitter
(iii)able to chemically combine with certain cells, and gamma emitter, short half life
(iv)gamma emitter, short half life
(v)chemically combines with blood cells, gamma emitter
(vi)chemically combines with other elements(maybe oxygen) + reacts with smoke?
(vii)chemically combines with cells that concentrate in thyroid.

pretty unsure, tell me where i went wrong ta

describe and account for the many uses of ethanol as a solvent for polar and nonpolar substances

 

[bored of sc]

taking a stab-

(i)gamma emitter
(ii)water soluble. gamma emitter
(iii)able to chemically combine with certain cells, and gamma emitter, short half life
(iv)gamma emitter, short half life
(v)chemically combines with blood cells, gamma emitter
(vi)chemically combines with other elements(maybe oxygen) + reacts with smoke?
(vii)chemically combines with cells that concentrate in thyroid.

I really unsure about most of these.

What I am vaguely sure about is:
(v) short half life
(vi) alpha emitter
(vii) gamma emitter, short half life

EDIT: Just realised there's an information section.

Possible answers are:
(i) beta/gamma emitter, 30 year half life
(iii) beta/gamma, 5.3 years
(v) gamma, 6 hours
(vi) alpha/gamma, 432 years
(vii) beta/gamma, 8 days

So you're on the money.