HSC 2012-2015 Chemistry Marathon (archive) (1 Viewer)

[Magical Kebab]

re: HSC Chemistry Marathon Archive

Properties of zeolite? Shit.

Not in syllabus.

 

[Riproot]

re: HSC Chemistry Marathon Archive

What is the catalyst used in catalytic cracking?

AND

a) Identify 3 properties of the catalyst that makes it useful
b) Describe 2 of them in relation to catalyst cracking (ie. why is this property useful for cat cracking?)

I'm sorry if it sounds weird, i dont know how to word questions xD

Zeolite?

It's like made of iron of something that give the reaction a surface to adsorb on other fun stuff...??

 

[bleakarcher]

re: HSC Chemistry Marathon Archive

Zeolite?

It's like made of iron of something that give the reaction a surface to adsorb on other fun stuff...??

hahahahhahahahhahahahah :')

 

[Riproot]

re: HSC Chemistry Marathon Archive

It's empirical. Could be which makes sense.

Ohhhh, yeah, lol

You can tell I'm in holiday mode.

 

[Riproot]

re: HSC Chemistry Marathon Archive

Not in syllabus.

they can ask stuff like why the catalyst is used and how it helps the reaction, but they wouldn't specify 3 things

 

[HeroicPandas]

re: HSC Chemistry Marathon Archive

Not in syllabus.

AWWWWW

Zeolite?

It's like made of iron of something that give the reaction a surface to adsorb on other fun stuff...??

Non-toxic
Large surface AREA- absorb a wide variety of reactants for cat cracking
High thermal stability- withstand the tempertures in cat cracking

 

[Sy123]

re: HSC Chemistry Marathon Archive

Increasing temperature?

Bingo, now explain mathematically and with words what exactly happens when temperature increases.

It doesn't exactly favour the hydronium ions more, that was just a silly mistake by me (I am pretty sure)

 

[Riproot]

re: HSC Chemistry Marathon Archive

Non-toxic
Large surface AREA- absorb a wide variety of reactants for cat cracking
High thermal stability- withstand the tempertures in cat cracking

I don't think being non-toxic is important at all though really.

and don't confuse adsorb and absorb

 

[DamTameNaken]

re: HSC Chemistry Marathon Archive

What is the catalyst used in catalytic cracking?

AND

a) Identify 3 properties of the catalyst that makes it useful
b) Describe 2 of them in relation to catalyst cracking (ie. why is this property useful for cat cracking?)

I'm sorry if it sounds weird, i dont know how to word questions xD

Zeolite catalyst

a) 1.Porous structure
2. Inorganic compound
3. Made from aluminium, oxygen and silicon (is that a property??)

b) 1. Porous structure - greater surface area means more room to react and act as a catalyst
2. Inorganic compound - organic compounds would be unable to survive the necessary temperatures of 500 degrees celsius

Everyone's asking really obscure questions today.

Question: Why does the melting and boiling points of alkanes and alkenes increase as the number of carbon atoms increases?

 

[bleakarcher]

re: HSC Chemistry Marathon Archive

Bingo, now explain mathematically and with words what exactly happens when temperature increases.

It doesn't exactly favour the hydronium ions more, that was just a silly mistake by me (I am pretty sure)

Well, we know that in order to decrease pH we must increase [H+]. To do this we must try to shift equilibrium to the left somehow. The auto-ionisation of water is endothermic so if we increase temperature the reverse reaction in the equilibrium reaction H3O(+)+OH(-)<->2H20 will be favoured to decrease the temperature by Le Chatelier's principle.

 

[Magical Kebab]

re: HSC Chemistry Marathon Archive

Zeolite catalyst

a) 1.Porous structure
2. Inorganic compound
3. Made from aluminium, oxygen and silicon (is that a property??)

b) 1. Porous structure - greater surface area means more room to react and act as a catalyst
2. Inorganic compound - organic compounds would be unable to survive the necessary temperatures of 500 degrees celsius

Everyone's asking really obscure questions today.

Question: Why does the melting and boiling points of alkanes and alkenes increase as the number of carbon atoms increases?

As the number of carbon atoms increases, the number of bonds present increases and also the number of electrons. This causes the molecule to become more polarized ie. more dipole dipole forces. Since this happens, a greater amount of energy is needed to break bonds and hence, a higher mp and bp.

Question: Describe a method by which transuranic elements can be synthesised. (2 marks)

 

[hayabusaboston]

re: HSC Chemistry Marathon Archive

As the number of carbon atoms increases, the number of bonds present increases and also the number of electrons. This causes the molecule to become more polarized ie. more dipole dipole forces. Since this happens, a greater amount of energy is needed to break bonds hence, a higher mp and bp.

Question: Describe a method by which transuranic elements can be synthesised. (2 marks)

dont forget by sheer molecular weight, dispersion forces are very large too.

Oh whoops I forgot I have to answer ur question, transuranic elements can be made from fusion reactions. this applies to all elements with atomic number greater than or equal to 96.

In this process a small positive nucleus or proton is accelerated in a charged particle accelerator
(also known as a cyclotron) which brings the proton or nucleus to the high speeds required to overcome the
positive repulsive force of the heavy nuclei (often of a previously made transuranic element) and fuse with
them.
A large quantity of transuranic elements can be produced this way, For example the
element hassium is produced by bombarding lead with iron.


Question: summarise the chemistry of the fermentation process

 

[Magical Kebab]

re: HSC Chemistry Marathon Archive

That's another reason.

 

[nightweaver066]

re: HSC Chemistry Marathon Archive

As the number of carbon atoms increases, the number of bonds present increases and also the number of electrons. This causes the molecule to become more (1) polarized ie. more dipole dipole forces. Since this happens, a greater amount of energy is needed to (2) break bonds (3) and hence, a higher mp and bp.

Question: Describe a method by which transuranic elements can be synthesised. (2 marks)

1. Alkanes & alkenes are non-polar (symmetrical structure). Intermolecular forces between alkane & alkene molecules are only dispersion forces. As there are more electrons with compounds having more electrons, there are stronger temporary induced dipoles so there'll be stronger dispersion forces.
2. Be more specific - intermolecular bonds!
3. State that melting point & boiling point are directly proportional to the degree/strength of intermolecular bonding between the molecules.

 

[Sy123]

re: HSC Chemistry Marathon Archive

Well, we know that in order to decrease pH we must increase [H+]. To do this we must try to shift equilibrium to the left somehow. The auto-ionisation of water is endothermic so if we increase temperature the reverse reaction in the equilibrium reaction H3O(+)+OH(-)<->2H20 will be favoured to decrease the temperature by Le Chatelier's principle.

Seems correct to me, nice work

As we increase temperature, our equilibrium constant value increases.
Remember that only is true for 25 degrees celsius

If we increase temperature, due to the various reasons mentioned above, we can arrive at and hence neutral water is at pH6. We can get that pH+pOh=12 because the equillibrium constant increases, to say rather than the normal -14 power.

 

[hayabusaboston]

re: HSC Chemistry Marathon Archive

That's another reason.

The dispersion forces? yu yea. Asnwer my question!

 

[bleakarcher]

re: HSC Chemistry Marathon Archive

As the number of carbon atoms increases, the number of bonds present increases and also the number of electrons. This causes the molecule to become more polarized ie. more dipole dipole forces. Since this happens, a greater amount of energy is needed to break bonds and hence, a higher mp and bp.

Question: Describe a method by which transuranic elements can be synthesised. (2 marks)

Neutron bombardment of non-fissile uranium-238 followed by beta decay of the new uranium isotope 239U to form neptunium-239.

238U92 + 1n0 -> 239U92

239U92 -> e- + 239Np93

 

[hayabusaboston]

re: HSC Chemistry Marathon Archive

1. Alkanes & alkenes are non-polar (symmetrical structure). Intermolecular forces between alkane & alkene molecules are only dispersion forces. As there are more electrons with compounds having more electrons, there are stronger temporary induced dipoles so there'll be stronger dispersion forces.
2. Be more specific - intermolecular bonds!
3. State that melting point & boiling point are directly proportional to the degree/strength of intermolecular bonding between the molecules.

good point nightweaver. I didnt notice that.

 

[bleakarcher]

re: HSC Chemistry Marathon Archive

Seems correct to me, nice work

As we increase temperature, our equilibrium constant value increases.
Remember that only is true for 25 degrees celsius

If we increase temperature, due to the various reasons mentioned above, we can arrive at and hence neutral water is at pH6. We can get that pH+pOh=12 because the equillibrium constant increases, to say rather than the normal -14 power.

yeah, I forgot K=10^(-14) for 25 degrees. Which was why I was so close minded lol.

 

[Magical Kebab]

re: HSC Chemistry Marathon Archive

1. Alkanes & alkenes are non-polar (symmetrical structure). Intermolecular forces between alkane & alkene molecules are only dispersion forces. As there are more electrons with compounds having more electrons, there are stronger temporary induced dipoles so there'll be stronger dispersion forces.
2. Be more specific - intermolecular bonds!
3. State that melting point & boiling point are directly proportional to the degree/strength of intermolecular bonding between the molecules.

Omg I suck