How do you determine the stronger base/acid?

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Ruth Rosales 3D
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How do you determine the stronger base/acid?

Postby Ruth Rosales 3D » Tue Dec 15, 2020 7:41 pm

Sometimes we were given a list of all strong acids but among them, I didn't really know how to determine which one was strongest.

Neel Sharma 3F
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Re: How do you determine the stronger base/acid?

Postby Neel Sharma 3F » Tue Dec 15, 2020 7:46 pm

To determine acid strength look first if there are strong acids in the list. All strong acids are relatively the same in strength so it is hard to differentiate among them. Next, look for two things resonance and an induction effect. If the conjugate base of the acid has resonance it is more stable and as a result, the acid is likely strong. The induction effect can be summarized as the force electronegative atoms have in delocalizing charge and stabilizing a molecule. Some induction rules include if a molecule has more oxygen's it is more stable and a stronger acid. Also, if acid is held together by a halogen, the strength of the acid will follow the increasing electronegativity of the halogen with fluorine at the top. Hope this helps!

Melanie Krahn 1C
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Re: How do you determine the stronger base/acid?

Postby Melanie Krahn 1C » Tue Dec 15, 2020 7:47 pm

I think it is helpful to be very familiar with a list of strong acids and bases and then those that are not found on either list can be classified as weak.

Ruth Rosales 3D
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Re: How do you determine the stronger base/acid?

Postby Ruth Rosales 3D » Tue Dec 15, 2020 8:03 pm

Melanie Krahn 1C wrote:I think it is helpful to be very familiar with a list of strong acids and bases and then those that are not found on either list can be classified as weak.


I mainly meant that in the question it is already known that all the acids/bases listed are strong but I have difficulty determining how to rank them from most to least acidic/basic. I understand where the confusion of my question is, I apologize.

Madeline Marron 1I
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Re: How do you determine the stronger base/acid?

Postby Madeline Marron 1I » Tue Dec 15, 2020 8:08 pm

I found it easier to just memorize the list of strong acids and bases

Lizbeth Garcia 1F
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Re: How do you determine the stronger base/acid?

Postby Lizbeth Garcia 1F » Tue Dec 15, 2020 9:51 pm

Memorizing the strong acids is a good help. Also, knowing that more oxygens usually mean stronger acids as well as higher electronegativity. There's also the idea that the easier it is to break the bond ,A-H, the stronger the acid is.

Izamary Marquez 2H
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Re: How do you determine the stronger base/acid?

Postby Izamary Marquez 2H » Tue Dec 15, 2020 9:53 pm

In addition to this, I was wondering if the relationship pH<pKa is ALWAYS true for weak acids, or if there are certain exceptions we should remember.

Astha Patel 2J
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Re: How do you determine the stronger base/acid?

Postby Astha Patel 2J » Tue Dec 15, 2020 9:59 pm

I would memorize the seven strong acids, because that rules out all the other acids as weak.
For the relative strengths of the weaker acids it depends on the acid type:
1) binary acids are some HA acid, where A is some anion. With these acids, the strength increases as the electron affinity of A increases (moving to the right of the period), and when the bond strength is lower (as you move down a period.
2) Oxoacids increase in strength when there are more oxygens present or the central atom is more electronegative. This is because the H-O bond becomes more polarized, increasing the partial positive charge on the H, making it easier to lose the H+.


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