-
Finished your HSC? Check out our University Discussion, Non-School forums or help out next year's HSC students! -
YOU can help the next generation of students in the community! Share your trial papers and notes on our Notes & Resources page
Prelim Chem Thread (2 Viewers)
- Thread starter drsabz101
- Start date
axwe7
Member
- Joined
- Aug 4, 2015
- Messages
- 183
- Gender
- Undisclosed
- HSC
- N/A
As far as I know, no there is no waste produced from fractional distillation of crude oil;
The only products produced from the separation of crude oil are; Residue, Kerosene, Diesel, Petroleum, Refinery Gas and Naptha, all of which have uses.
https://www.google.com.au/url?sa=i&...yIn_OfWnbhl_gcmOn9QBURTQ&ust=1454577012754182
The only products produced from the separation of crude oil are; Residue, Kerosene, Diesel, Petroleum, Refinery Gas and Naptha, all of which have uses.
https://www.google.com.au/url?sa=i&...yIn_OfWnbhl_gcmOn9QBURTQ&ust=1454577012754182
leehuan
Well-Known Member
- Joined
- May 31, 2014
- Messages
- 5,805
- Gender
- Male
- HSC
- 2015
Sorry, didn't see this - This is simply because the allotrope of carbon - graphite - is electrically conductive. (If one used diamond, however, there'd be problems.)
leehuan
Well-Known Member
- Joined
- May 31, 2014
- Messages
- 5,805
- Gender
- Male
- HSC
- 2015
This is concerning.
An ionic bond is formed when one atom effectively gives another one some of it's electrons. The most simple case is sodium chloride (table salt), NaCl. In this case, Na has an electron configuration of 2,8,1 whereas Cl has an electron configuration of 2,8,7
An atom will always seek to complete it's outer shell, or discard it. So here, the sodium atom donates that 1 electron in it's valence shell to the chlorine atom.
The sodium atom lost an electron, so now it becomes the sodium ion - [Na+]
The chlorine atom gained an electron, so now it becomes the chloride ion - [Cl-]
__________________
A covalent bond is formed when atoms start sharing electrons between each other. In effect, this electron that has been shared is now capable of orbiting both atoms in question. The most simple case is water, H2O, where the elements existing are oxygen (electron config. 2, 6) and hydrogen (electron config 1.)
Oxygen and hydrogen both seek to fill it's outer shell (valence shell). Hence, oxygen and hydrogen will each share one electron with one another, thereby forming a covalent bond. The overall result is that two electrons are orbiting both H, AND O.
Because oxygen technically requires two electrons, it will form a covalent bond with two hydrogen molecules. This allows oxygen to also fill it's outer shell. (Note that hydrogen only requires one)
On the contrary I can understand if this is nonsensical at the start.
In a covalent network, we are once again interested in covalent bonding.
To illustrate a covalent network, we will consider carbon, which has electron configuration 2,4.
Carbon technically needs FOUR electrons to fill it's outer shell. One way of doing this, is to just form two covalent bonds with oxygen molecules. But that's not gonna make a covalent network.
Another way, is just to share all 4 electrons with another carbon atom. But that, will be exhaustive.
Instead, what carbon does is that it will interact with FOUR OTHER carbons.
Two carbon atoms will each share one electron with each other. However, what will happen is that every carbon shares an electron with four other carbons. Because this allows carbon to gain all 4 other electrons, it also completes it's outer shell.
But, ALL the carbons in the lattice will do this; not just that one carbon. So because you have one carbon forming covalent bonds with four other carbons, AND SO ON, we have a covalent network
Last edited:
Hey, I got a question about the separation technique crystallisation. Can somebody please elucidate my understanding of this process. I still feel that I'm not too sure of how it works. What I think of how it works is:
Technique of crystalisation - difference in solubilities
Start with two solids which are soluble in a liquid, but each of them only dissolve at different temperatures in that liquid.
The mixture of the solids are dissolved in hot (almost boiling) liquid, and will dissolve, form a solution. This solution is then cooled down (placed in ice bath).
One of the solids would only be soluble if the temperature of the liquid was very high. Since the mixture is cooled down, this solid will solidify? (I think it does) and will crystalise, free from impurities, as it is no longer soluble with it in low temperature.
This mixture is then filtered out through filtration. The remaining mixture, however, still contains little amounts of that solid, uncrystalized and still dissolved in it
So this process repeats again, until all the desired pure solid is obtained.
Sorry if its too much to ask. Thankyou.
Technique of crystalisation - difference in solubilities
Start with two solids which are soluble in a liquid, but each of them only dissolve at different temperatures in that liquid.
The mixture of the solids are dissolved in hot (almost boiling) liquid, and will dissolve, form a solution. This solution is then cooled down (placed in ice bath).
One of the solids would only be soluble if the temperature of the liquid was very high. Since the mixture is cooled down, this solid will solidify? (I think it does) and will crystalise, free from impurities, as it is no longer soluble with it in low temperature.
This mixture is then filtered out through filtration. The remaining mixture, however, still contains little amounts of that solid, uncrystalized and still dissolved in it
So this process repeats again, until all the desired pure solid is obtained.
Sorry if its too much to ask. Thankyou.
Shuuya
Well-Known Member
- Joined
- Sep 3, 2015
- Messages
- 833
- Gender
- Undisclosed
- HSC
- 2016
A mole of a substance contains 6.022 x 10^23 units
eg. a mole of H2O contains 6.022 x 10^23 H2O molecules
leehuan
Well-Known Member
- Joined
- May 31, 2014
- Messages
- 5,805
- Gender
- Male
- HSC
- 2015
It's ionic. So
[K+] is left as is
[Cl-] however, yes you would draw 7 dots, and one cross around the Cl, THEN put in the negative charge.
The one cross is entirely optional. But I do it to show that that extra electron came from Potassium.
eyeseeyou
Well-Known Member
You will rarely get tested on that because that's not as important as other parts in the chemical earth (lewis dot diagram, chemical equations) but you still will get tested on it