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April 29, 2024, 11:21:24 pm

Author Topic: HSC Chemistry Question Thread  (Read 1048102 times)  Share 

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onepunchboy

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Re: Chemistry Question Thread
« Reply #930 on: October 22, 2016, 09:56:31 am »
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Oh ok thanks rui!

Neutron

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Re: Chemistry Question Thread
« Reply #931 on: October 22, 2016, 08:15:43 pm »
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Hey hey! Bit rusty with POM but just with this question:

"Compare the process of polymerisation of ethylene and glucose. Include relevant chemical equations in your answer." (3 marks)

What more do they want us to say apart from the fact that ethylene is addition polymerisation and glucose is condensation? :o like did we ever learn/need to know the specifics to condensation polymerisation? All I know is that it's when two difunctional monomers join together and eliminate a small molecule, I don't really know much about the 'process' :/ And with ethylene do we need to go into zieggler natta and free radical polymerisation (for HDPE and LDPE) ? And what equations do they even want omg (do they want the n(glucose)--> (cellulose)n + (n-1) water? With the actual equations ofc i just cbb to type it out) this whole question just confuses me hahahaha cheers

Neutron

RuiAce

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Re: Chemistry Question Thread
« Reply #932 on: October 22, 2016, 08:22:27 pm »
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Hey hey! Bit rusty with POM but just with this question:

"Compare the process of polymerisation of ethylene and glucose. Include relevant chemical equations in your answer." (3 marks)

What more do they want us to say apart from the fact that ethylene is addition polymerisation and glucose is condensation? :o like did we ever learn/need to know the specifics to condensation polymerisation? All I know is that it's when two difunctional monomers join together and eliminate a small molecule, I don't really know much about the 'process' :/ And with ethylene do we need to go into zieggler natta and free radical polymerisation (for HDPE and LDPE) ? And what equations do they even want omg (do they want the n(glucose)--> (cellulose)n + (n-1) water? With the actual equations ofc i just cbb to type it out) this whole question just confuses me hahahaha cheers

Neutron
You do actually need to know the whole process. That's what you're comparing.

Only similarity is probably that they're both polymerisation processes. The differences are in the processes themselves.

Ethylene undergoes addition polymerisation, which MUST have an initiator or Ziegler-Natta catalyst (can't be spontaneous). The three phases are initiation+activation, propagation and termination.

Glucose undergoes condenstion polymerisation, in which beta-glucose monomers join together flipping, and also always expels the water molecule. Two monomers join to form a dimer, and then these dimers undergo the polymerisation process.

But no great depth is needed here though.

onepunchboy

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Re: Chemistry Question Thread
« Reply #933 on: October 23, 2016, 03:49:42 pm »
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Hello! can anyone explain why propane is more volatile than propan-1-ol, propanoic acid and methyl propanoate?
this is for a multiple choice questions

thanks in adv :)

jakesilove

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Re: Chemistry Question Thread
« Reply #934 on: October 23, 2016, 04:11:15 pm »
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Hello! can anyone explain why propane is more volatile than propan-1-ol, propanoic acid and methyl propanoate?
this is for a multiple choice questions

thanks in adv :)

Hey! Volatility is about how easily something evaporates. Unlike the other substances listed, Propane doesn't have strong hydrogen/dipole-dipole bonds. It's also much smaller than the other molecules. As such, it doesn't 'bind' to itself very strongly (ie. weak intermolecular bonds), and so less energy is required to break them apart/evaporate Propane!

Does that make sense?
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onepunchboy

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Re: Chemistry Question Thread
« Reply #935 on: October 23, 2016, 04:30:31 pm »
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Yes thank you so much :)

onepunchboy

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Re: Chemistry Question Thread
« Reply #936 on: October 24, 2016, 11:07:02 am »
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Hello!

Can anyone help me out with this Q : " explain , in terms of intermolecular bonding forces involved, why esters are only slightly soluble in water, even though the chemicals used in its manufacture are soluble"?

i thought esters were actually quite soluble because of (-OH) but idk
Thanks!

sweetcheeks

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Re: Chemistry Question Thread
« Reply #937 on: October 24, 2016, 11:20:57 am »
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Hello!

Can anyone help me out with this Q : " explain , in terms of intermolecular bonding forces involved, why esters are only slightly soluble in water, even though the chemicals used in its manufacture are soluble"?

i thought esters were actually quite soluble because of (-OH) but idk
Thanks!
The chemicals used to make the ester (acid and alcohol) both have -OH groups allowing them to form hydrogen bonds with the water molecules. When the reaction occurs, the ester does not contain any -OH groups and can not form hydrogen bonds. The ester only has a COO group which has slight dipole-dipole forces, making the molecule less polar than its constituents.

jakesilove

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Re: Chemistry Question Thread
« Reply #938 on: October 24, 2016, 11:25:27 am »
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The chemicals used to make the ester (acid and alcohol) both have -OH groups allowing them to form hydrogen bonds with the water molecules. When the reaction occurs, the ester does not contain any -OH groups and can not form hydrogen bonds. The ester only has a COO group which has slight dipole-dipole forces, making the molecule less polar than its constituents.

Exactly right! I don't really have anything to add; clearly identify WHY substances are soluble in certain solutions, and then outline the factors above to come to the required conclusion. Let us know if we can clarify anything!
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noonedoesnt

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Re: Chemistry Question Thread
« Reply #939 on: October 24, 2016, 08:44:48 pm »
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Confusing question

RuiAce

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Re: Chemistry Question Thread
« Reply #940 on: October 24, 2016, 08:47:23 pm »
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Confusing question
Use process of elimination

A) Does ethylene become cellulose? Lol no wtf
B) Does ethylene become ethanol? Yes - use hydration. Does ethanol get polymerised? Lol no wtf
C) Does ethylene become glucose? Lol no wtf
D) Does ethylene become styrene? Yes - use addition reaction. Does styrene get polymerised? Yes it becomes polystyrene.

Therefore D

noonedoesnt

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Re: Chemistry Question Thread
« Reply #941 on: October 24, 2016, 08:48:47 pm »
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Yeah thanks rui, it's what I thought but I didn't understand what the question meant. Had a mind blank, thanks.

noonedoesnt

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Re: Chemistry Question Thread
« Reply #942 on: October 25, 2016, 12:59:20 pm »
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Another question, can i get help with part C. Regards.

Biology24123

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Re: Chemistry Question Thread
« Reply #943 on: October 25, 2016, 01:10:18 pm »
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Another question, can i get help with part C. Regards.

Divide the energy found in part b by the heat of combustion of hydrogen (convert to KJ)
Then use PV=nRT formula to find the volume of hydrogen

noonedoesnt

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Re: Chemistry Question Thread
« Reply #944 on: October 25, 2016, 01:31:14 pm »
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what is PV = nRT?