I'm confused (Acids/Bases)

In summary: Just that's not something to "suppose", that's a definition of an acid (more precisely: Arrhenius definition, there are other, more general definitions).
  • #1
HazyMan
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The question says: A solution of highly acidic HA is given, with a molarity of 1M. Is it true that [A-]>[H3O+] or not? I simply don't understand why the hydronium is mentioned and i don't know how to find the molarity of these two individually.
 
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  • #2
What is an acid?

What does it mean "highly acidic" in the context of water solution?
 
  • #3
Borek said:
What is an acid?

What does it mean "highly acidic" in the context of water solution?
acid= substance with pH<7

solution of highly acidic HA= a highly acidic substance is solute in water?
 
  • #4
HazyMan said:
acid= substance with pH<7

No, pH is not a property of an acid. It is property of a solution. Oxalic acid is a solid and as such it has no pH, yet it is still an acid.

How is pH defined?

Why is it lower than 7 when there is an acid present?
 
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  • #5
Borek said:
No, pH is not a property of an acid. It is property of a solution. Oxalic acid is a solid and as such it has no pH, yet it is still an acid.

How is pH defined?

Why is it lower than 7 when there is an acid present?
Sorry for being late, i believe pH is derived as the negative logarithm of the acid's molarity (moles of H+ divided by the solution's volume)

I suppose that the acid is being dissolved in the water, releasing H+ ions. This might be wrong (aswell as the H+/V derivation i mentioned in the previous parenthesis perhaps) because i don't know if these ions will react with the water in the solution.
 
  • #6
HazyMan said:
I suppose that the acid is being dissolved in the water, releasing H+ ions.

Yes. Just that's not something to "suppose", that's a definition of an acid (more precisely: Arrhenius definition, there are other, more general definitions).

Ignoring water (the solvent) for a moment, what can you tell about concentrations of H+ and A-? (think in terms of stochiometry, try to write reaction equation of HA dissociation).
 
  • #7
I think the equation is HA->H+ & A- .

Obviously 1 mol of HA gives 1 mol of H+ and 1 mol of A- so the mole number of H+ and A- are equal. Since there is no change in volume, the concetrations of H+ and A- should also be equal. Therefore [H3O+]=[A-].

What confused me about the original question was the hydronium, but i later found out that it's the same thing as H+, something that i still can't understand quite so well but I've accepted it.
 
  • #8
HazyMan said:
I think the equation is HA->H+ & A- .

Obviously 1 mol of HA gives 1 mol of H+ and 1 mol of A-

Only if the dissociation went to completion. That's not always the case.

so the mole number of H+ and A- are equal

That would actually hold always, when there are no other sources of H+.

Since there is no change in volume, the concetrations of H+ and A- should also be equal. Therefore [H3O+]=[A-].

That's approximately correct, but you have also dissociating water.

What confused me about the original question was the hydronium, but i later found out that it's the same thing as H+, something that i still can't understand quite so well but I've accepted it.

To some extent H+ and H3O+ are equivalents. See https://en.wikipedia.org/wiki/Hydronium
 
  • #9
That's approximately correct, but you have also dissociating water.

What exactly does that mean?
 
  • #10
There is more than one source of hydronium in the solution. Told you that in the other thread.
 
  • #11
Borek said:
There is more than one source of hydronium in the solution. Told you that in the other thread.
Is that other source the water solvent?
 
  • #12
Yes.
 

1. What is the difference between acids and bases?

Acids are substances that have a pH level lower than 7 and donate hydrogen ions in a solution. Bases, on the other hand, have a pH level higher than 7 and accept hydrogen ions in a solution.

2. How do acids and bases react with each other?

When an acid and a base are mixed together, they undergo a neutralization reaction. This means that the acidic and basic properties cancel each other out, resulting in a neutral solution.

3. What are some common examples of acids and bases?

Some common examples of acids include lemon juice, vinegar, and stomach acid. Bases can be found in substances such as baking soda, soap, and ammonia.

4. Can acids and bases be harmful to our health?

Yes, some acids and bases can be harmful to our health if not handled properly. For example, strong acids and bases can cause burns on the skin and damage to the respiratory system if inhaled.

5. How do we measure the strength of an acid or base?

The strength of an acid or base is measured on the pH scale, which ranges from 0 to 14. A lower pH indicates a stronger acid, while a higher pH indicates a stronger base. A pH of 7 is considered neutral.

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