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VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: physics on November 05, 2010, 09:41:15 pm

Title: molecular and ionic equations?
Post by: physics on November 05, 2010, 09:41:15 pm
I'm confused on wat this is asking. in kilbaha 2009 where they give Hcl and NaOH they ask
write the balanced molecular equation:

Hcl+naOH = H20 + Nacl

then they ask for the ionic equation?
then i have no idea

the ans is h3o+   + oh- ==> 2h2o or H+    + OH- --> H2O

totally lost! someone help!
Title: Re: molecular and ionic equations?
Post by: 98.40_for_sure on November 05, 2010, 09:59:36 pm
Break up all the compounds into their constituent ions, eg. HCl becomes H+ and Cl-
then cancel out the ones on both sides and you are left with what is called the 'ionic equation'
Title: Re: molecular and ionic equations?
Post by: cameron_15 on November 05, 2010, 10:01:18 pm
Break the aqueous molecules up into their Ions, re-write equation in this broken up form (Definitely not the technical name) then cancel anything that is the same on both sides (Spectator Ions). This will give you the second equation.

The first one given is just the standard ionization of water, which is obviously occurring as there is an acid in water...

Both of these are legitimate ionic equations that are occurring.

Hope that helps in some way...
Title: Re: molecular and ionic equations?
Post by: physics on November 05, 2010, 10:17:04 pm
i dont get it still?
if you break it up dont they all cancel out each other because all i did was rearrange the reactants to get hte products????????
Title: Re: molecular and ionic equations?
Post by: 98.40_for_sure on November 05, 2010, 10:19:33 pm
HCl + NaOH => H2O + NaCl

becomes

H+     +    Cl-      + Na+     + OH-     => H2O    +     Na+    +    Cl-

As there are Na+ and Cl- on both sides, they cancel out leaving you with the ionic equation that is:

H+ + OH- => H2O
Title: Re: molecular and ionic equations?
Post by: physics on November 05, 2010, 10:21:38 pm
THIS IS WHAT i get out of it :(
Title: Re: molecular and ionic equations?
Post by: 98.40_for_sure on November 05, 2010, 10:23:21 pm
Noooo dude H2O doesn't become H+ H+ OH-. you can't split a liquid
Title: Re: molecular and ionic equations?
Post by: physics on November 05, 2010, 10:25:16 pm
i have another unrealated question. kilbaha 2009 asks why in galvanic anode is negatve and why cathode is negative in electrolytic? iono. because thye said so!!!!!???
do we needa know this?

Why doesnt the Na Cl cancel each other then? i dont get it
Title: Re: molecular and ionic equations?
Post by: luken93 on November 05, 2010, 10:29:34 pm
Okay so your equation is:

HCl (aq) + NaOH (aq)   --->   H2O (l) + NaCl(aq)

Therefore, when broken up it becomes:

H+(aq)  + Cl-(aq) + Na+(aq) + OH-(aq)   --->   2H+(l) + O2-(l) + Na+(aq) + Cl-(aq)

Therefore, cancel out the elements that do not change state:

H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq)   --->   2H+(l) + O2-(l) + Na+(aq) + Cl-(aq)

Hence you are left with:
H+(aq) + OH-(aq)   --->   2H+(l) + O2-(l)

H+(aq) + OH-(aq)   --->   H2O(l)
Title: Re: molecular and ionic equations?
Post by: physics on November 05, 2010, 10:31:15 pm
Quote from: luken93 on November 05, 2010, 10:29:34 pm
Okay so your equation is:

HCl (aq) + NaOH (aq)   --->   H2O (l) + NaCl(aq)

Therefore, when broken up it becomes:

H+(aq)  + Cl-(aq) + Na+(aq) + OH-(aq)   --->   2H+(l) + O2-(l) + Na+(aq) + Cl-(aq)

Therefore, cancel out the elements that do not change state:

H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq)   --->   2H+(l) + O2-(l) + Na+(aq) + Cl-(aq)

Hence you are left with:
H+(aq) + OH-(aq)   --->   2H+(l) + O2-(l)

H+(aq) + OH-(aq)   --->   H2O(l)

OH WOW SO SMART! THANKS MAN!
Title: Re: molecular and ionic equations?
Post by: 98.40_for_sure on November 05, 2010, 10:33:31 pm
Quote from: physics on November 05, 2010, 10:31:15 pm
Quote from: luken93 on November 05, 2010, 10:29:34 pm
Okay so your equation is:

HCl (aq) + NaOH (aq)   --->   H2O (l) + NaCl(aq)

Therefore, when broken up it becomes:

H+(aq)  + Cl-(aq) + Na+(aq) + OH-(aq)   --->   2H+(l) + O2-(l) + Na+(aq) + Cl-(aq)

Therefore, cancel out the elements that do not change state:

H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq)   --->   2H+(l) + O2-(l) + Na+(aq) + Cl-(aq)

Hence you are left with:
H+(aq) + OH-(aq)   --->   2H+(l) + O2-(l)

H+(aq) + OH-(aq)   --->   H2O(l)

OH WOW SO SMART! THANKS MAN!

Gee thanks... i guess his sub/superscript rendition appeals to the mentally challenged slightly more than my effigy of a firing squad line-up.
Title: Re: molecular and ionic equations?
Post by: luken93 on November 05, 2010, 10:34:32 pm
Quote from: physics on November 05, 2010, 10:25:16 pm
i have another unrealated question. kilbaha 2009 asks why in galvanic anode is negatve and why cathode is negative in electrolytic? iono. because thye said so!!!!!???
do we needa know this?

Why doesnt the Na Cl cancel each other then? i dont get it
http://www.youtube.com/watch?v=A0VUsoeT9aM
Title: Re: molecular and ionic equations?
Post by: luken93 on November 05, 2010, 10:35:32 pm
Haha no worries, it can take a while to understand until it finally clicks!
Title: Re: molecular and ionic equations?
Post by: physics on November 05, 2010, 10:37:07 pm
Quote from: luken93 on November 05, 2010, 10:34:32 pm
Quote from: physics on November 05, 2010, 10:25:16 pm
i have another unrealated question. kilbaha 2009 asks why in galvanic anode is negatve and why cathode is negative in electrolytic? iono. because thye said so!!!!!???
do we needa know this?

Why doesnt the Na Cl cancel each other then? i dont get it
http://www.youtube.com/watch?v=A0VUsoeT9aM
I DONT get it :( explain please =D....do we even needa know this??!
Quote from: 99.95_for_sure on November 05, 2010, 10:33:31 pm
Quote from: physics on November 05, 2010, 10:31:15 pm
Quote from: luken93 on November 05, 2010, 10:29:34 pm
Okay so your equation is:

HCl (aq) + NaOH (aq)   --->   H2O (l) + NaCl(aq)

Therefore, when broken up it becomes:

H+(aq)  + Cl-(aq) + Na+(aq) + OH-(aq)   --->   2H+(l) + O2-(l) + Na+(aq) + Cl-(aq)

Therefore, cancel out the elements that do not change state:

H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq)   --->   2H+(l) + O2-(l) + Na+(aq) + Cl-(aq)

Hence you are left with:
H+(aq) + OH-(aq)   --->   2H+(l) + O2-(l)

H+(aq) + OH-(aq)   --->   H2O(l)

OH WOW SO SMART! THANKS MAN!

Gee thanks... i guess his sub/superscript rendition appeals to the mentally challenged slightly more than my effigy of a firing squad line-up.
thanks for trying.ur awesome too =D
Title: Re: molecular and ionic equations?
Post by: luken93 on November 05, 2010, 10:52:35 pm
Well from what I have understood from Yr 11 Chem:

The more electronegative ion will pull e- from the less electronegative ion
Therefore, in the case of that video, Copper is more e/n than Zinc

Hence Copper Ions will take electrons from Zinc, according to the equation:
Cu2+(aq) + 2e- ---> Cu(s)
This is a reduction reaction.

According the the Term RED CAT
ie. REDuction occurs at the CAThode

Hence at the Anode, oxidation of Zinc occurs according to the equation:
Zn(s) ---> Zn2+(aq) + 2e-