Chemical Equations for Acids and bases -write as ions?

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Sophia Stewart 3F
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Joined: Wed Sep 30, 2020 9:48 pm

Chemical Equations for Acids and bases -write as ions?

Postby Sophia Stewart 3F » Sat Dec 12, 2020 9:59 am

While doing the textbook problems, I have come across some acid/base equations where the product is written out with the H+ separated from the strong acid, and others where they would be together. Does this notation matter?

For example, with problem J.9, is is just as correct to write KOH+CH3COOH-> H2O + K+ + CH3CO2- as if it was written KCH3CO2?

And what about when you have salts in water (an equation going the other direction)? Would the product be written broken down by its charges too? For example, J.17 a) NaC6H50 + H20-> NaOH + C6H5OH or Na+ + OH- ....

Hopefully that question makes sense.

Zaid Bustami 1B
Posts: 105
Joined: Wed Sep 30, 2020 9:48 pm
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Re: Chemical Equations for Acids and bases -write as ions?

Postby Zaid Bustami 1B » Sat Dec 12, 2020 3:42 pm

I think I answered something similar in another topic right here, might be helpful to look at too https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=57&t=69400&sid=f39e3f22a505137e8fd07240f943ce1c.
Basically the idea is that for things that completely dissolve in water, writing either both of the components together or separated is correct. Take HCl. Since it's a strong acid, it completely dissociates in water and gives rise to the ions H+ and Cl-. Writing HCl in the equation is as correct as writing H+ + Cl-. The only thing is though is that we know HCl is dissolved in solution and not just a solid, so you'd need to make sure that you write HCl(aq) to be fully correct. The same goes for the ions: you'd want to write H+(aq) and Cl-(aq).
However, there is only one correct way to write weak acids like acetic acid (CH3COOH). Because it's weak it only partially dissociates in water, so writing it as CH3COOH- + H+ is incorrect. You'd want to leave it at CH3COOH(aq) since it only partially dissociates into its ions.
So because KCH3CO2 completely dissociates in water (it is soluble), it is just as correct to write K+ + CH3CO2- as if it was written KCH3CO2. By the same token, NaOH is just as correct as Na+ + OH-. Just keep in mind all of these should technically be labeled as (aq), but I think for simplicity it's left out.


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