Module 2 questions (1 Viewer)

[Xayma]

Originally posted by Wohzazz
when does this state occur, is it just like Al ions in water? maybe when you have a metal oxide in an acid solution?

Yes its because they are ions, water is a polar substance, due to its bonds not being linear (due to Oxygen having a higher electronegativity), it forms polar bond to the water molecules and so isnt attracted to the other ion anymore.

 

[Xayma]

Originally posted by Wohzazz
so what about the semi metal like i mentioned? do you have to add them up?
my thoughts for Ga(2) O(3), each Ga give 3 electrons (6 total) to the 3 O. therefore they add up

Gallium is more likely to ionicly bond.

Originally posted by Wohzazz
i suppose you can deduce it from Xayma's 2 non metals form covalent bonds

They wont always seem to add up to fill all gaps, covalent bonding can get weird, for example Carbon Monoxide.

 

[Wohzazz]

so many exceptions *stressed*
so how many exceptions are there?
and Ga is not the only semi metal, how can you tell?

 

[Xayma]

Originally posted by Wohzazz
and Ga is not the only semi metal, how can you tell?

Because Gallium isnt considered a metalloid/semi-metal Only boron, silicon, germanium, arsenic, antimony, and tellurium are and polonium is normally considered one as well.

 

[abdooooo!!!]

Originally posted by Wohzazz
so many exceptions *stressed*
so how many exceptions are there?
and Ga is not the only semi metal, how can you tell?

in short you can't... unless you have the electronegativity values of the two elements that is bonding. generally electronegativity has to be more than 1.7 in difference for a ionic bond. the reasons are rather simple because the pull of one on another's electrons is too strong when is more than 1.7 so they form two ions held together by their opposing charges.

 

[Wohzazz]

well what happens to the semi-metals? do they covalently bond or ionically bond?

 

[abdooooo!!!]

Originally posted by Xayma
Because Gallium isnt considered a metalloid/semi-metal Only boron, silicon, germanium, arsenic, antimony, and tellurium are and polonium is normally considered one as well.

LOL. ... but its close

 

[Wohzazz]

Originally posted by abdooooo!!!
in short you can't... unless you have the electronegativity values of the two elements that is bonding. generally electronegativity has to be more than 1.7 in difference for a ionic bond. the reasons are rather simple because the pull of one on another's electrons is too strong when is more than 1.7 so they form two ions held together by their opposing charges.

i remember reading this somewhere, hmm, but do they always give you the electronegativities in exam conditions?

 

[Xayma]

Originally posted by Wohzazz
well what happens to the semi-metals? do they covalently bond or ionically bond?

Mainly Ionically, however whether they take electrons or have electrons taken from them varies depending on the other element.

 

[Wohzazz]

Originally posted by Xayma
Yes its because they are ions, water is a polar substance, due to its bonds not being linear (due to Oxygen having a higher electronegativity), it forms polar bond to the water molecules and so isnt attracted to the other ion anymore.

missed reading this, so you are saying that water's polarity makes it be attracted to the Al ion rather than to another water molecule
in 'the other ion anymore', which ion are you referring to?

 

[abdooooo!!!]

Wohzazz man, this is the hsc... you don't need to understand anything. if you get lucky you'll proly get 2 or 3 math/chem questions at most and they are so freakin easy that anyone can do. the rest is just evaluating and discussing hard issues like fuel prices.

Originally posted by Wohzazz
What i mean is for an reaction, do you write
acid + base= salt + water
or base + acid = water + salt
just was wondering if there was any conventions

i don't know... but i generally write acid + base= salt + water. since 'a'cid comes before 'b'ase... you know abcdefg....

you always write salt first because water is always water if you know what i mean... like when you do indefinite intergrals, the c, is always written last. but there are special cases of no water.

Originally posted by Xayma
They wont always seem to add up to fill all gaps, covalent bonding can get weird, for example Carbon Monoxide.

ya thats because they are super crazy coordinate covalent bonds that bond in practically anyway

 

[Wohzazz]

Originally posted by Xayma
Mainly Ionically, however whether they take electrons or have electrons taken from them varies depending on the other element.

more exceptions, i hate exceptions in chemistry, always forget them

 

[Xayma]

Originally posted by Wohzazz
in 'the other ion anymore', which ion are you referring to?

Aluminium wont form ions on its own, you need to have something strip it of its electrons, which will become an ion as well and will be dissolved in water.

 

[Wohzazz]

Originally posted by abdooooo!!!
Wohzazz man, this is the hsc... you don't need to understand anything. if you get lucky you'll proly get 2 or 3 math/chem questions at most and they are so freakin easy that anyone can do. the rest is just evaluating and discussing hard issues like fuel prices.

think i worry too much, but i just don't want to trip over if any easy stuff from the preliminary is indirectly asked
personally i'd say maths questions are all easy , you just got to watch out for numbers and units

 

[Xayma]

Originally posted by Wohzazz
more exceptions, i hate exceptions in chemistry, always forget them

If a metalloid bonds with an group I metal, it will act like the non-metal (ie take electrons) but if it bonds with a Halogen it will act like a metal (ie lose electrons) not sure what happens when the get closer, but I doubt you will have something difficult like that.

 

[abdooooo!!!]

hey i just realised i have this pretty fab aussie site that has the periodic table with electronegativity, here it is if you're interested: http://www.ausetute.com.au/bondpola.html

it should teach you the basics...

 

[Wohzazz]

Originally posted by Xayma
Aluminium wont form ions on its own, you need to have something strip it of its electrons, which will become an ion as well and will be dissolved in water.

so for aquated aluminium, is it Al.(H2O)3 or something like that
so the aluminium is not actually bonded to the H2O, it's only the polar nature of water that make it attracted to aluminium even though it's not an ion

 

[Xayma]

Originally posted by Wohzazz
is it Al.(H2O)3

Thats hydrated aluminium, which I dont think will form. Aluminium will only dissolve in water if its an ion. If its in its natural state the metallic bonds are too strong and it is neutral so the polar water molecules would be more attracted to themselves then the aluminium

 

[abdooooo!!!]

Originally posted by Wohzazz
edit/ deleted 'not' in q 4
4/

Here's an example from Chem Context 2
2. The reaction for the production of water gas is
C(s) + H2O(g) 6 (double arrows) CO(g) + H2(g)
if the system is at equilibrium, what would be the effect of the following changes
I) the concentraion of all the species, and
answer: concentrations of H2O , CO and H2 will decrease but concentration of C(s) will remain constant

hey whats the '6' before the equilbrium sign ( <----> ), and whats the question mean? change in the concentration of all the species to what? by what means?

 

[Wohzazz]

6 was a typo,
i forgot to write the rest of the question
edited now