# chemical equation

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• February 29th, 2008, 06:21 PM
icu
chemical equation
Hey, i am new here, how do u get the product in a chemical equation?
like 2Mg + O2 --> 2MgO

can anyone explain how u get the 2MgO?
and i hv tryed to search for the answer in sites

thanks in advance
• February 29th, 2008, 06:37 PM
rancidchickn
You have to have the same number of each element on both sides of the equation.
• February 29th, 2008, 06:41 PM
organic god
do you mean how you get MgO

or how you get the amount of it like balancing the numbers?

in the first question. because thats how it reacts put simply.
magnesium + oxygen goes to MgO

in the second question. you have to look at number of atoms on each side of the equation and balance it.
you cant change small numbers like the 2 in O2.
but you can add any number to the front of a molecule to make it balance
• February 29th, 2008, 07:32 PM
icu
i already know how to balance it, for instance:

C2H6 + O2 --> ?

like this for example, how do u get the product?

and thanks heaps for yr help :-D
• February 29th, 2008, 11:16 PM
rancidchickn
It depends on what's reacting. C2H6 (ethane) is a hydrocarbon and you are combusting it (you know this from the O2). Therefore the products are going to be CO2 and H2O.

2C2H6 + 7O2 --> 4CO2 + 6H2O
• March 1st, 2008, 02:33 AM
icu
how do u know that u get H2O and CO2?
• March 1st, 2008, 11:30 AM
Bunbury
If you had fewer than 7 moles of oxygen per 2 moles of ethane you would produce some CO as well as or instead of CO2, partial oxidation being a widespread industrial process. At some dilution (too much ethane or too much oxygen) the reaction wouldn't even start. So your question is a good one and the simple answer is we know from experience what will happen. I suspect you're looking for a more fundamental answer though, which I can't provide.
• March 1st, 2008, 11:44 AM
free radical
Quote:

Originally Posted by icu
how do u know that u get H2O and CO2?

because it is a combustion. you need to recognise reactants and the sorts of reactions they predict; you can't get it all if you just think of them as letters and numbers. Salts dissolve, acids and bases dissociate, that sort of thing.

based on rancidchickens answer above, can you work out what happens when you metabolise glucose?

C6H12O6 + O2 -->

(you'll need to balance both sides)
• March 1st, 2008, 02:40 PM
icu
ok, correct me if i am wrong :oops:

but is it C6H12O6 + 6O2 --> 6CO2 + 6H2O

like acid + oxygen --> carbon dioxide + water
• March 1st, 2008, 04:26 PM
free radical
Quote:

Originally Posted by icu
ok, correct me if i am wrong :oops:

but is it C6H12O6 + 6O2 --> 6CO2 + 6H2O

like acid + oxygen --> carbon dioxide + water

The equation is right, but glucose is not an acid, it's a carbohydrate ... (carbohydrate=hydrated carbon, see?)

Good job on balancing the equation though!
• March 1st, 2008, 11:53 PM
icu
ty free radical, but what makes a carbohydrate=hydrated carbon?

for example acid is an acid because it has hydrogen ions in them, and bases have hydroixde ion in them so what about carohydrate?

thanks in advance :-D
• March 2nd, 2008, 06:43 AM
organic god
Quote:

acid is an acid because it has hydrogen ions in them, and bases have hydroixde ion in them
not strictly correct.

there are many different definitions for acid and bases.
i think what you're talking about is a bronsted-lowry acid/base

in this case an acid is a proton (H+) donator
whereas a base is a proton (H+) acceptor.

this explains why ammonia (NH3) is a base. it accepts H+ to form the
NH4+ ion
• March 2nd, 2008, 01:47 PM
icu
[quote="organic god"]
Quote:

acid is an acid because it has hydrogen ions in them, and bases have hydroixde ion in them
not strictly correct.

so this is wrong, the teacher taught me this? and what makes a carbohydrate=hydrated carbon?

thanks
• March 2nd, 2008, 06:14 PM
organic god
you're teacher probably taught you a simplified version.

the correct version is acid is H+ donator, base is H+ acceptor,
ask your teacher
• March 2nd, 2008, 08:10 PM
free radical
[quote="icu"]
Quote:

Originally Posted by organic god
Quote:

acid is an acid because it has hydrogen ions in them, and bases have hydroixde ion in them
not strictly correct.

so this is wrong, the teacher taught me this? and what makes a carbohydrate=hydrated carbon?

thanks

It's sort of a mnemonic to help you. A carbohydrate is, technically, more or less defined as having a stoichiometry of C:H:O of 1:2:1.

Water (this is your hydration) has a stoichiometry of H:O of 2:1 (H2O). So, if a carbohydrate is (CH2O)n then it is a hydrated (H2O) carbon (C).

CH2O = carbo-hydrate.

Carbohydrates are burned by you when you exercise, to make energy. You need oxygen to burn things, including carbohydrates.

Sugar is C6H12O6, or (CH2O)6, but there are other carbohydrates as well, loads of them. And any of them combined with oxygen will give you CO2 and H2O, and you just have to balance the equations.

Hydrocarbons (ethane, like in your second post) also burn in the presence of oxygen. This is why rancidchicken said that the O2 is an indication of a combustion (burning).... and so now you might recognise these sorts of reactions more easily?

Acids and bases are different, buffers are different, etc etc - you'll probably be busy learning different types of reactions for a while but it sounds like you are picking it up which is great.

[/list]
• March 2nd, 2008, 11:54 PM
icu
hey thanks, and can anyone explain why here has a bracket?

Mg2 + OH- ---> Mg(OH)s

thanks :-D
• March 3rd, 2008, 01:16 PM
organic god
you sure you got that equation right?

the bracket is there to show there is 2 lots of (OH), not 2 hydrogens
• March 3rd, 2008, 10:28 PM
icu
ya, but why does here have bracket?

Fe3 + OH- ---> Fe(OH)3

and here doesn't here have bracket?

Cu + CO23 ---> Cu2CO3

thanks :D
• March 3rd, 2008, 11:08 PM
rancidchickn
Quote:

Fe3 + OH- ---> Fe(OH)3
Btw this should be:
Fe + 3OH- ---> Fe(OH)3

The brackets mean you have three -OH's. OH is a polyatomic ion.

Quote:

Cu + CO23 ---> Cu2CO3
I don't know what you're trying to do here. It's not balanced right.

You should just grab a chemistry text book and take a look at it. You'll probablly understand this much better than someone can explain to you on a forum.
• March 3rd, 2008, 11:19 PM
icu
but isn't iron is Fe3+?

thanks :D :-D :) :(
• March 3rd, 2008, 11:27 PM
rancidchickn
Yes. Iron is Fe3+ (in that case), so you need 3 OH-'s to get a 0 charge.
• March 3rd, 2008, 11:30 PM
Bunbury
I think you might be confused about valence which is usually indicated as a superscript, and the number of ions in a molecule which is usually indicated by a subscript. I don't think we can show sub and superscripts on here (?).

Magnesium hydroxide is Mg(OH)2. The bracket means you need 2 OH- ions for one Mg++ ion to make a stable molecule. Magnesium has a +2 valence. The hydroxide ion has a -1 valence. The pluses and minuses have to balance. As organic god wrote, the bracket followed by the 2 is to show there are two OH- ions in the molecule.

Ferric iron has a +3 valence so you need three OH- ions to balance, hence Fe(OH)3.

Copper has a +2 valence and the carbonate ion has a -2 valence, so you only need one of each to balance and you don't need brackets because you don't have to indicate multiple carbonate ions. The correct formula is CuCO3.
• March 3rd, 2008, 11:47 PM
icu
how about this?

H + CO23?

thanks
• March 3rd, 2008, 11:50 PM
icu
Quote:

Originally Posted by icu
how about this?

H + CO23 ---> H2CO3?

this dont equal a 0 charge?

thanks

• March 4th, 2008, 07:10 AM
sunshinewarrior
Quote:

Originally Posted by Bunbury
I think you might be confused about valence which is usually indicated as a superscript, and the number of ions in a molecule which is usually indicated by a subscript. I don't think we can show sub and superscripts on here (?).

Magnesium hydroxide is Mg(OH)2. The bracket means you need 2 OH- ions for one Mg++ ion to make a stable molecule. Magnesium has a +2 valence. The hydroxide ion has a -1 valence. The pluses and minuses have to balance. As organic god wrote, the bracket followed by the 2 is to show there are two OH- ions in the molecule.

Ferric iron has a +3 valence so you need three OH- ions to balance, hence Fe(OH)3.

Copper has a +2 valence and the carbonate ion has a -2 valence, so you only need one of each to balance and you don't need brackets because you don't have to indicate multiple carbonate ions. The correct formula is CuCO3.

Mg<sup>+2</sup> + 2OH<sup>-1</sup> = Mg(OH)<sub>2</sub> ?

Just use the < instead of the [ and it works with "sup" and "/sup" and so on.
• March 4th, 2008, 08:22 PM
Bunbury
Quote:

just use the < instead of the [ and it works with "sup" and "/sup" and so on.
Thanks sunshine, I did not know that.

Quote:

how about this?

H + CO23?
How about this: H<sup>+</sup> + CO<sub>3</sub><sup>2-</sup>

How many hydrogens do you need to get zero charge?
• March 4th, 2008, 09:53 PM
icu
two? :oops:

thanks
• March 4th, 2008, 11:16 PM
icu
i think i got it :D
you will need 2 hydrogen to get a zero charge therefore the equation is

H2+ + CO3- ---> H2CO3

correct me if i am wrong :oops:

Thanks :D
• March 4th, 2008, 11:26 PM
Bunbury
Right, you need two hydrogens. But the equation isn't balanced until you have the two hydrogens on the left side.

2H<sup>+</sup> + CO<sub>3</sub><sup>2-</sup> ---> H<sub>2</sub>CO<sub>3</sub>
• March 4th, 2008, 11:42 PM
icu
cool,can u tell me why it cant be on the right side? because isn't hydrogen a diatomic atom H2?or does it only apply to superscript not subscript?

thanks :D
• March 5th, 2008, 12:07 AM
Bunbury
If you put the 2 on the right hand side of the H as in H<sub>2</sub> you are describing a molecule of hydrogen, which is diatomic, and is electrically neutral. It is not then an ion, it is two atoms bonded together.
• March 5th, 2008, 01:53 AM
icu
ok, thanks bunbury, do u have any examples that has a bracket in it, i want to see if i have got it or not :-D

thanks
• March 5th, 2008, 10:09 AM
Bunbury
Look up ammonium sulfate (sulphate).
• March 5th, 2008, 09:52 PM
icu
NH4 + SO24 ---> NH4(SO24)

is it right?

thanks :-D
• March 5th, 2008, 09:54 PM
rancidchickn
NH4 has a positive charge (NH4+). And what do you mean by SO24? 4SO2?
• March 5th, 2008, 11:08 PM
icu
i dont know, i am trying to work out the chemial equation for ammonium sulfate (sulphate).

one day my teacher were talking about predicting charges eg. Na= 2,8,1 = Na+, P = 2,8,5 = P-3 etc....
and then she said that Si= 2,8,4 can equal Si-4 or Si+4, and i think she said it depends on the bond, can anyone tell me which one is right and more about this...

much appercaited, thanks :-D
• March 7th, 2008, 02:22 PM
icu
correct me if i am wrong....

2Na + O2 ---> Na2O

so what i am doing here is that to balance the superscript of O and the subscript of Na? correct? so we put two on the left hand side of Na?

Al + 3Cl ---> AlCl3

so over here do we balance the superscript of Al and the subscript of Cl?

thanks
• March 7th, 2008, 07:45 PM
Bunbury
Quote:

2Na + O2 ---> Na2O

so what i am doing here is that to balance the superscript of O and the subscript of Na? correct? so we put two on the left hand side of Na?
Perhaps the notation convention has changed in the 40 years since I did this, but it's a little confusing to write about superscripts and subscripts when you put everything on the same line. I think if you mean this you are correct:

2Na<sup>+</sup> + O<sup>2-</sup> = Na<sub>2</sub>O

Try to use the code that sunshinewarrior explained so we can all talk the same language.
• March 7th, 2008, 09:24 PM
icu
ok, i use to know how to do it but i forgot :oops:
• March 8th, 2008, 05:08 AM
sunshinewarrior
Quote:

Originally Posted by icu
ok, i use to know how to do it but i forgot :oops:

It's easy. As I said earlier:

Quote:

Mg+2 + 2OH-1 = Mg(OH)2 ?

Just use the < instead of the [ and it works with "sup" and "/sup" and so on.
If this seems too elliptical, most coding we use here uses the square brackets [ and ]. If, however, you use the chevrons (for want of a better word) < and > to start and end a code, "sup" for superscript and "sub" for subscript, then you should find it quite easy.
• March 8th, 2008, 03:08 PM
icu
like this?
Cu<2
• March 8th, 2008, 05:36 PM
Bunbury
No, like this

Code:

`Cu<sup>2+</sup>`
and

Code:

`SO<sub>4</sub><sup>2-</sup>`
• March 9th, 2008, 12:10 AM
icu
ok thanks heaps guys :-D

one day my teacher were talking about predicting charges eg. Na= 2,8,1 = Na<sup>+</sup>, P = 2,8,5 = P<sup>-3</sup> etc....
and then she said that Si= 2,8,4 can equal Si<sup>-4</sup> or Si<sup>+4</sup>, and i think she said it depends on the bond, can anyone tell me which one is right and more about this...

much appercaited, thanks
• March 9th, 2008, 12:32 AM
icu
hi :)

correct me if i am wrong....

Na<sup>+</sup> + O<sup>2-</sup> ---> Na<sub>2</sub>O

so what i am doing here is that to balance the superscript of O with the subscript of Na? correct? so we put two on the left hand side of Na?

Al<sup>3+</sup> + Cl<sup>-</sup> ---> AlCl<sup>3</sup>

so over here do we balance the superscript of Al with the subscript of Cl?

thanks
• March 10th, 2008, 12:46 PM
sunshinewarrior
Quote:

Originally Posted by icu
ok thanks heaps guys :-D

one day my teacher were talking about predicting charges eg. Na= 2,8,1 = Na<sup>+</sup>, P = 2,8,5 = P<sup>-3</sup> etc....
and then she said that Si= 2,8,4 can equal Si<sup>-4</sup> or Si<sup>+4</sup>, and i think she said it depends on the bond, can anyone tell me which one is right and more about this...

much appercaited, thanks

Silicon, carbon etc, have half-filled shells of 8, which means they can be considered to be either having 4 extra, or 4 fewer electrons than are necessary to fill their shells. As a result of this, they have special properties (including organic chemistry, silicons affinity for 'doping' and so on). Whether they behave as +4 or -4 will therefore depend upon circumstance.

Steve F or other better chemists can correct any serious errors of mine.
• March 11th, 2008, 02:02 AM
icu
cool, np thanks for your help anyway :D
• March 12th, 2008, 08:53 AM
sunshinewarrior
Quote:

Originally Posted by icu
hi :)

correct me if i am wrong....

Na<sup>+</sup> + O<sup>2-</sup> ---> Na<sub>2</sub>O

so what i am doing here is that to balance the superscript of O with the subscript of Na? correct? so we put two on the left hand side of Na?

Al<sup>3+</sup> + Cl<sup>-</sup> ---> AlCl<sup>3</sup>

so over here do we balance the superscript of Al with the subscript of Cl?

thanks

Ideally you'd write the first equation as:

2Na<sup>+</sup> + O<sup>2-</sup> = Na<sub>2</sub>O

The valences on the left side need to cancel each other out, and the number of atoms on the left and right sides need to balance each other out. In fact, you'd be encouraged to write it (if it didn't become so cumbersome) as:

4Na<sup>+</sup> + O<sub>2</sub><sup>2-</sup> = 2Na<sub>2</sub>O

This is because we tend to use molecular oxygen (O<sub>2</sub>), rather than single atoms (O), in chemical reactions and this way makes the equation more realistic.

Using this convention, your second equation is probably best written as:

Al<sup>3+</sup> + 3Cl<sup>-</sup> = AlCl<sub>3</sub>

Does this help?

Edit: Ooops. Edited for typo.
• March 12th, 2008, 09:48 AM
Bunbury
‘ang on a minute.

Please correct me if I’m wrong (it’s been about a million years since I did this in school), but the oxygen molecule has all its shells filled by virtue of the covalent bond between the two oxygen atoms, so it’s not correct to show an oxygen molecule with a valency. The molecule has no charge. You’d write the reaction equation without the valencies thus:

4Na + O<sub>2</sub> = 2Na<sub>2</sub>O

innit?
• March 12th, 2008, 11:57 AM
sunshinewarrior
Quote:

Originally Posted by Bunbury
‘ang on a minute.

Please correct me if I’m wrong (it’s been about a million years since I did this in school), but the oxygen molecule has all its shells filled by virtue of the covalent bond between the two oxygen atoms, so it’s not correct to show an oxygen molecule with a valency. The molecule has no charge. You’d write the reaction equation without the valencies thus:

4Na + O<sub>2</sub> = 2Na<sub>2</sub>O

innit?

You're right, of course. I was waiting for one of you knowledgeable buggers to show I'd been gassing. But what about the Sodium valence then?

Ah heck... icu can have fun figuring it out, eh?
• April 18th, 2008, 05:27 PM
Behr_25
whats a mole? :D
• April 19th, 2008, 06:55 AM
thyristor
Mole is a unit for particles.
If you have a mole of particles it means that you have Avogadros number of the particles, i.e. approximately 6*10<sup>23</sup>
• May 5th, 2008, 09:44 PM
raed
Mole : is the molecular or atomic weight expressed in grams