January 25, 2021, 03:28:22 AM
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Topic: Questions on Acids and Bases  (Read 423 times)

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Offline PicturesOfLilly

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Questions on Acids and Bases
« on: January 11, 2021, 06:08:43 PM »
I don't expect anyone to answer them all. Every bit helps though!

1. Take a solution of ethanoic acid in water; Is the acidity level of such a solution based on the acidity of the molecule, or the quantity of the molecule? If the 5% solution is more acidic, then I would have to ask the following... if the forward and reverse reactions are taking place at the same rate, then doesn't this mean that there would be the same amount of conjugate base molecules in solution as there is acid molecules? So how is it considered an acidic solution if there's the same amount of base in it as there is acid?

2. In a video I recently watched about the pH of amino acids, I heard the following being said. "We can think of an acidic solution as having lots of excess protons". I can understand that a solution that has had an acid put into it, would have lots of excess protons. But if all the protons have been "donated", then how can it be considered an acid. This is something that's always confused me.

3. It's said that when acids and bases react in the right proportions, that neutralisation occurs. Is it poss for this to occur if one of the two (either the acid or the base) is neutral, and therefore only acting as a base/acid. Say with the case of ethanoic acid and water.

4. Does the neutralisation of an acid and a base always have to involve water? My chemistry book seems to suggest it does. If so, what about the reaction of [ammonia + HCl → ammonium chloride]? Is this considered a neutralisation reaction?

5. Regarding the above eqn to form ammonium chloride; it is said that this is an example of how Arrhenius's definition is limited as such a reaction would not be considered an acid base reaction. But since it is considered an acid base reaction, then this means that any two molecules (that both contain H) which combine to give one molecule, can be considered an acid and a base beforehand? Doesn't that mean that almost anything could be considered an acid or a base.

6. Is [HCl + NH3 → NH4Cl] one of the few examples of acid base reactions that has only one molecule on the right hand side? Is this more common for with acid/base reactions when water isn't involved?

7. Although there is no reverse reaction, what is the conj base of NaHCO3 in the eqn: [HCl + NaHCO3 → NaCl + H2O + CO2]?? Is it CO2 or H2O? Or is there none?

Thank you
« Last Edit: January 11, 2021, 06:33:22 PM by PicturesOfLilly »

Online Borek

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Re: Questions on Acids and Bases
« Reply #1 on: January 12, 2021, 03:07:35 AM »
Please read the forum rules.
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Offline AWK

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Re: Questions on Acids and Bases
« Reply #2 on: January 12, 2021, 04:53:48 AM »
As for your dilemmas about ammonia basicity, they stem from little historical information in modern textbooks.
Arrhenius created in 1884 (Ph.D. dissertation) a theory of acids and bases in aqueous solutions based on the electrical conductivity of solutions of weak acids and bases, and there was a need to write the ammonia formula as a base because Lewis and Brønsted theories (both from 1923) were not yet available. Analogously to NaOH, chemists began to write down the formula for ammonia in an aqueous solution as NH4OH.
In 1916, Lewis published his Octet Rule, and the above formula of ammonia became "chemical heresy." To avoid this problem, a solution of ammonia in water was introduced as NH3(aq) or NH3·H2O. In Lewis and Brønsted's theories, this "chemical prosthesis" was no longer needed.
All amines, hydroxylamines, hydrazines, and PH3 react similarly to ammonia (PH3 only in non-aqueous solutions).
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Offline PicturesOfLilly

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Re: Questions on Acids and Bases
« Reply #3 on: January 17, 2021, 03:41:01 PM »
As for your dilemmas about ammonia basicity, they stem from little historical information in modern textbooks.
Arrhenius created in 1884 (Ph.D. dissertation) a theory of acids and bases in aqueous solutions based on the electrical conductivity of solutions of weak acids and bases, and there was a need to write the ammonia formula as a base because Lewis and Brønsted theories (both from 1923) were not yet available. Analogously to NaOH, chemists began to write down the formula for ammonia in an aqueous solution as NH4OH.
In 1916, Lewis published his Octet Rule, and the above formula of ammonia became "chemical heresy." To avoid this problem, a solution of ammonia in water was introduced as NH3(aq) or NH3·H2O. In Lewis and Brønsted's theories, this "chemical prosthesis" was no longer needed.
All amines, hydroxylamines, hydrazines, and PH3 react similarly to ammonia (PH3 only in non-aqueous solutions).

Thank you for your reply. It's a bit complex for me. I'm not sure if there's an answer to my question in there, but does a neutralisation reaction have to involve water?

Offline PicturesOfLilly

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Re: Questions on Acids and Bases
« Reply #4 on: January 17, 2021, 03:43:16 PM »
Please read the forum rules.
I have tried to get answers to these questions before posting here.

Offline Meter

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Re: Questions on Acids and Bases
« Reply #5 on: January 18, 2021, 02:56:44 AM »
Common misconception, but an equilibrium does not imply that the reactants and products exist in equal concentrations. The equilibrium constant (K) is a measure for the distribution of the reactants and products respectively. In the case of ethanoic acid, its equilibrium reaction is heavily favored for the protonated form. If you are referring to the concentration of H3O+ and acetate ions present in the solution, then yes, these would in the case of acetic acid be in equal concentrations, but pH is a measure of H3O+ activity alone.




Offline Babcock_Hall

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Re: Questions on Acids and Bases
« Reply #6 on: January 18, 2021, 01:20:53 PM »
Please read the forum rules.
I have tried to get answers to these questions before posting here.
You need to show your attempts or give your thoughts before we can help you.

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