Reaction of acetic acid (CH3COOH) with potassium hydroxide (KOH)

[TheAbsoluTurk]

Homework Statement

Balance the following equation and write the corresponding
ionic and net ionic equation (if appropriate):

CH$_{3}$COOH $_{(aq)}$+ KOH $_{(aq)}$ $\rightarrow$

Homework Equations

None as far as I know.

The Attempt at a Solution

I wrote:

CH$_{3}$COOH $_{(aq)}$+ KOH $_{(aq)}$ $\rightarrow$ CH$_{3}$COOK $_{(aq)}$ + H$_{2}$O $_{(l)}$

But this is the wrong answer.

I don't understand why K$^{+}$ does not form a compound with CH$_{3}$COO$^{-}$. Can anyone tell what concept or law/theorem controls what compounds form and what compounds do not form? Why is K$^{+}$ a spectator ion in this reaction?

 

[Borek]

Your reaction equation is OK, it just doesn't answer the question - you were asked to write ionic and net ionic reactions. Which of the compounds present in the reaction will be fully dissociated?

Note: format indices in your formulae with [noparse] and [/noparse] tags, not with LaTeX. And state of matter should be normal text, on the same level as the formula (so dissolved potassium acetate is [noparse]CH₃COOK(aq)[/noparse] - rendered as CH₃COOK(aq)).

 

[TheAbsoluTurk]

Your reaction equation is OK, it just doesn't answer the question - you were asked to write ionic and net ionic reactions. Which of the compounds present in the reaction will be fully dissociated?

Note: format indices in your formulae with [noparse] and [/noparse] tags, not with LaTeX. And state of matter should be normal text, on the same level as the formula (so dissolved potassium acetate is [noparse]CH₃COOK(aq)[/noparse] - rendered as CH₃COOK(aq)).

So my initial line of thinking was:

Molecular Equation:
CH₃COOH (aq)+ KOH (aq) → CH₃COOK (aq) + H₂O (l)

Ionic Equation:

CH₃COO^- (aq) + H⁺ (aq) + K⁺ (aq) + OH^- (aq) → CH₃COO^- + K⁺ + H₂O (l)

Net Ionic Equation:

H⁺ (aq) + OH^- (aq) → H₂O (l)

This is incorrect.

But I reasoned that CH₃COO^- is a weak acid so all of the things in the textbook about not dissociating 100% must come into play here.

Therefore,

Molecular Equation:
CH₃COOH (aq)+ KOH (aq) → CH₃COOK (aq) + H₂O (l)

Ionic Equation:

CH₃COOH (aq) + K⁺ (aq) + OH^- (aq) → CH₃COO^- +K⁺ + H₂O (l)

Net Ionic Equation:

CH₃COOH (aq) + OH^- (aq) → CH₃COO^- + H₂O (l)

That is correct according to the answers in the text.

How come CH₃COO^- and K⁺ do not form a compound though? Is there anyway to calculate or know why? Is it because CH₃COOH is not dissociated 100% in solution? (it is a weak acid.)

Thanks for the help with writing the equations.

 

[TheAbsoluTurk]

In the ionic equation, K+ and CH3COO- are dissociated because CH3COOK is a strong electrolyte. While CH3COOK is a weak acid so it doesn't dissociate 100%.

Is this correct. I'm surprised the text doesn't explain this. Borek, can you recommend any comprehensive, first year university chemistry textbooks?

 

[Borek]

How come CH₃COO^- and K⁺ do not form a compound though?

Imagine a solution containing equal concentrations of CH₃COO^-, Cl^-, K⁺ and Na⁺ - you can't tell what compounds it contains, there is more than one answer. So we don't name these compounds at all, it is safer to simply list ions.

Sorry, I can't be of much help when it comes to books - unless you are interested in Polish ones Chang and Pauling are usually praised as good titles.

 

[TheAbsoluTurk]

Imagine a solution containing equal concentrations of CH₃COO^-, Cl^-, K⁺ and Na⁺ - you can't tell what compounds it contains, there is more than one answer. So we don't name these compounds at all, it is safer to simply list ions.

Sorry, I can't be of much help when it comes to books - unless you are interested in Polish ones Chang and Pauling are usually praised as good titles.

So the explanation that "In the ionic equation, K+ and CH3COO- are dissociated because CH3COOK is a strong electrolyte. While CH3COOH is a weak acid so it doesn't dissociate 100%." is incorrect? Or it doesn't make sense?

I'm reading Chang right now actually.

 

[TheAbsoluTurk]

In the ionic equation, K+ and CH3COO- are dissociated because CH3COOK is a strong electrolyte. While CH3COOK is a weak acid so it doesn't dissociate 100%.

Is this correct. I'm surprised the text doesn't explain this. Borek, can you recommend any comprehensive, first year university chemistry textbooks?

I meant to say CH3COOH is a weak acid, not CH3COOK. My idea is that CH3COOK is a strong electrolyte so it dissociates 100% in solution therefore leaving K+ and CH3COO- in solution.

 

[Borek]

I meant to say CH3COOH is a weak acid, not CH3COOK. My idea is that CH3COOK is a strong electrolyte so it dissociates 100% in solution therefore leaving K+ and CH3COO- in solution.

This part was OK, I just tried to answer your other question.

 

[TheAbsoluTurk]

This part was OK, I just tried to answer your other question.

Oh, ok. I thought the two questions answered the same thing. Anyway I have a better idea of how to tell what products will arise from certain reactants. Thank you for the help.