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Topic: Predicting Acid-Base Equations (Is this Correct)  (Read 4089 times)

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Offline RyanG

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Predicting Acid-Base Equations (Is this Correct)
« on: November 15, 2010, 06:26:03 PM »
Question: Small quantities of the poisonous hydrocyanic acid can be produced in a research lab by quantitatively reacting sodium cyanide and hydrochloric acid. Predict the acid-base reaction.

This is what I did:

NaCN(aq) + HCl(aq)  :rarrow:
-----
NaCN(aq)  :rarrow: Na+ (aq) + CN- (aq)

HCl(aq)  :rarrow: H3O+ (aq) + Cl- (aq)
-----

H3O+ (aq) + CN- (aq)  ::equil:: H2O (l) + HCN (aq)

H3O+ (aq) is stronger than HCN (aq) , therefore equilibrium favors the products.

Is this correct? If anybody can reply quick, that would be great. I have a quiz on these tom, and want to know if I am doing this right. Thanks

Offline Grundalizer

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Re: Predicting Acid-Base Equations (Is this Correct)
« Reply #1 on: November 15, 2010, 06:28:01 PM »
Yeah that's correct.

The summarized reaction (which I'm guessing would be good enough for the quiz) would be NaCN + HCl  :rarrow: NaCl + HCN

Offline RyanG

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Re: Predicting Acid-Base Equations (Is this Correct)
« Reply #2 on: November 15, 2010, 06:38:53 PM »
Thank you.

Also does anybody know when to use

 ::equil::

compared to

 :rarrow:

My teacher said something like, if you have a strong acid then you would use  :rarrow:

Offline Grundalizer

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Re: Predicting Acid-Base Equations (Is this Correct)
« Reply #3 on: November 15, 2010, 06:46:43 PM »
The  ::equil:: denotes an equilibrium arrow in which the chemical species can go back and forth between the molecules on either side of the arrows, as in

H2O + H+ ::equil:: H3O+      (This can go back and forth in solution)


Or a permanent arrow  :rarrow: like

CH4 2O2 :rarrow:  2H2O + CO2   This is a chemical reaction which is "permanent" in a sense, can't just turn CO2 and water into methane

Offline chsteven

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Re: Predicting Acid-Base Equations (Is this Correct)
« Reply #4 on: November 15, 2010, 06:47:27 PM »
Yeah it looks good! ;D

Offline RyanG

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Re: Predicting Acid-Base Equations (Is this Correct)
« Reply #5 on: November 15, 2010, 06:51:03 PM »
The  ::equil:: denotes an equilibrium arrow in which the chemical species can go back and forth between the molecules on either side of the arrows, as in

H2O + H+ ::equil:: H3O+      (This can go back and forth in solution)


Or a permanent arrow  :rarrow: like

CH4 2O2 :rarrow:  2H2O + CO2   This is a chemical reaction which is "permanent" in a sense, can't just turn CO2 and water into methane

Thank you, makes a little more sense. But how do you know what arrow to use in these types of equations.

Offline Grundalizer

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Re: Predicting Acid-Base Equations (Is this Correct)
« Reply #6 on: November 15, 2010, 07:29:04 PM »
That's a very good question.  When I was a younger student in Highschool I used to wonder how my teacher knew what arrow to use.  To tell you the truth, I don't have a good answer, but I'll try.  It really comes from experience.  In general, any resonance structure of solvation of a compound will have the  ::equil:: arrows.

If you have reagents A + B turning into C + D then it'll probably be  :rarrow:

I keep thinking about it, and it is a really good basic question, but I just don't have an answer.  At this point I just intuitavley know which arrows to put up but can't explain it, and I usually pride myself in being able to explain chemistry to people.

In reality though,  :larrow: denotes the more realistic happenings of the chemical reaction, because even if JUST ONE SINGLE MOLECULES out of billinos upon billions reacts to form product A, then you can use the equilibrium arrow, but in that case people usually draw a longer right or left arrow then the one beneath it, to denote that ONE SIDE IS FAVORED which is sometimes the case. 


Offline RyanG

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Re: Predicting Acid-Base Equations (Is this Correct)
« Reply #7 on: November 15, 2010, 07:33:12 PM »
That's a very good question.  When I was a younger student in Highschool I used to wonder how my teacher knew what arrow to use.  To tell you the truth, I don't have a good answer, but I'll try.  It really comes from experience.  In general, any resonance structure of solvation of a compound will have the  ::equil:: arrows.

If you have reagents A + B turning into C + D then it'll probably be  :rarrow:

I keep thinking about it, and it is a really good basic question, but I just don't have an answer.  At this point I just intuitavley know which arrows to put up but can't explain it, and I usually pride myself in being able to explain chemistry to people.

In reality though,  :larrow: denotes the more realistic happenings of the chemical reaction, because even if JUST ONE SINGLE MOLECULES out of billinos upon billions reacts to form product A, then you can use the equilibrium arrow, but in that case people usually draw a longer right or left arrow then the one beneath it, to denote that ONE SIDE IS FAVORED which is sometimes the case. 



Haha, I know what you mean. Ill just use the  ::equil:: on the test, since 95% of the examples done in class had them.

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