Lewis acids and Bases

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MichaelMendozaD1F
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Lewis acids and Bases

Postby MichaelMendozaD1F » Sun Nov 15, 2020 4:21 pm

How do you classify if a compound is a Lewis acid or base when given the chemical formula?

Rylee Mangan 1K
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Re: Lewis acids and Bases

Postby Rylee Mangan 1K » Sun Nov 15, 2020 4:22 pm

Draw the Lewis structure to see if all the atoms have a complete octet. If not, for example Boron in BF3, then that would be an acid.

Nathan Tong 3G
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Re: Lewis acids and Bases

Postby Nathan Tong 3G » Sun Nov 15, 2020 4:25 pm

The same applies with Lewis bases, if a molecule has lone pair electrons that it can donate, such as F-, then it is a Lewis base.

Tatyana Bonnet 2H
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Re: Lewis acids and Bases

Postby Tatyana Bonnet 2H » Sun Nov 15, 2020 4:28 pm

To help classify them you would have to draw out the lewis structure. The molecule/compound that does not have a complete octet will readily accept electrons making it the acid. The molecule with lone pairs able to give away will be the base. Like the example during one of the lectures, BF3 drawn out shows B not having a complete octet and is missing a pair of electrons. It would accept electrons making it the acid. F- has it's full octet of lone pairs and can donate a pair to BF3 to make B have its full octet, making F- the base as it is the electron donor.

Ryan Agcaoili 2E
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Re: Lewis acids and Bases

Postby Ryan Agcaoili 2E » Sun Nov 15, 2020 4:28 pm

One way to identify a lewis base is by drawing the lewis structure of it. If the compound is electron deficient, then it is a lewis base because it needs to accept electrons. A lewis base usually is an anion or has extra electrons, which can be donated to lewis bases.

Lesly Lopez 3A
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Re: Lewis acids and Bases

Postby Lesly Lopez 3A » Sun Nov 15, 2020 4:28 pm

Hi,
You draw the Lewis structure and look for a pair of electrons that can form a bond to another atom. A Lewis base is a molecule or ion that can donate a pair of electrons to form a bond. An atom, ion, or molecule with a lone-pair of electrons can be a Lewis base. I like to draw out my compounds to see how they would work. I am a visual learner hope it helps.

Jonathan Banh 1G
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Re: Lewis acids and Bases

Postby Jonathan Banh 1G » Sun Nov 15, 2020 4:40 pm

I think the most important distinction here is to determine whether a substance is more likely to act as an electron-pair acceptor or donor. If it acts as an electron-pair acceptor, you would consider it as a Lewis acid. On the other hand, if it acts an electron-pair donor, you would consider it as a Lewis base. Like Rylee said, BF3 is a Lewis acid because boron does not have a full octet, meaning it is electron-deficient. Thus, it is more likely to act as an electron-pair acceptor in reactions. As a result, you can consider this substance as a Lewis acid.

Shivani Kapur 2J
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Re: Lewis acids and Bases

Postby Shivani Kapur 2J » Sun Nov 15, 2020 5:02 pm

After drawing out the lewis pair structure, see if the molecule or compound has a lone pair that it can give or if it needs a lone pair to become an octet. For example, the electrons in NH3 can give its electron pair to BF3, which is electron deficient therefore NH3 is the lewis base and BF3 is the lewis acid.

Jonathan3B
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Re: Lewis acids and Bases

Postby Jonathan3B » Sun Nov 15, 2020 6:07 pm

A lewis base donates electrons in a chemical reaction while lewis acids accept electrons.

Jaden Joodi 3J
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Re: Lewis acids and Bases

Postby Jaden Joodi 3J » Sun Nov 15, 2020 6:13 pm

After drawing the lewis dot structure, there is an unfilled octet, then it is a lewis acid. If there is a lone pair, it is a lewis base.

Sarah Huang 3A
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Re: Lewis acids and Bases

Postby Sarah Huang 3A » Sun Nov 15, 2020 6:14 pm

MichaelMendozaD1F wrote:How do you classify if a compound is a Lewis acid or base when given the chemical formula?


Hi Michael! I had the same issue that you had in classifying the compounds, especially in Sapling.

However, a quick note that might make it easier for you is that lewis acids are atoms that accept or take electrons from other compounds, basically meaning that lewis acids usually include, but not limited to metal cations, electron-deficient molecules, or molecules with polar bonds that accept electrons. To put simply, Lewis acids are basically cations.

Lewis bases on the other hand are electron donors, and if Lewis acids tend to be cations, then that means Lewis bases are anions, as in electronegative molecules or molecules with lone pairs, such as NH3. Although the overall charge is 0 for the molecule, NH3 still has the lone pair on the Nitrogen with three bonds to the Hydrogens.

If you want to find out whether a chemical formula is an anion or cation, I suggest that you find the formal charge of the atoms and the overall charge of the molecule!

I really hope that helps because it definitely clarified a lot for me!

Diana Aguilar 3H
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Re: Lewis acids and Bases

Postby Diana Aguilar 3H » Sun Nov 15, 2020 8:08 pm

I was also having a hard time with the classification of Lewis Acids and Bases, so I'm glad you asked. Thank you so much to everyone for the clarification, it was very helpful!

Hannah Chang 3K
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Re: Lewis acids and Bases

Postby Hannah Chang 3K » Sun Nov 15, 2020 8:10 pm

Lewis acids are electron acceptor; lewis bases are electron donor

Mariah Disc 2C
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Re: Lewis acids and Bases

Postby Mariah Disc 2C » Sun Nov 15, 2020 8:17 pm

One way to determine this is to draw out the Lewis structure. If the octets are not complete it is an acid.

Jenaye Brelland 2I
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Re: Lewis acids and Bases

Postby Jenaye Brelland 2I » Sun Nov 15, 2020 8:55 pm

Tatyana Bonnet 3H wrote:To help classify them you would have to draw out the lewis structure. The molecule/compound that does not have a complete octet will readily accept electrons making it the acid. The molecule with lone pairs able to give away will be the base. Like the example during one of the lectures, BF3 drawn out shows B not having a complete octet and is missing a pair of electrons. It would accept electrons making it the acid. F- has it's full octet of lone pairs and can donate a pair to BF3 to make B have its full octet, making F- the base as it is the electron donor.

Your comment was actually very helpful! Thank you. I was a little confused by how we can know if it will accept electrons or not. I get it now.

MichaelMendozaD1F
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Re: Lewis acids and Bases

Postby MichaelMendozaD1F » Mon Nov 16, 2020 8:34 pm

Sarah Huang 3A wrote:
MichaelMendozaD1F wrote:How do you classify if a compound is a Lewis acid or base when given the chemical formula?


Hi Michael! I had the same issue that you had in classifying the compounds, especially in Sapling.

However, a quick note that might make it easier for you is that lewis acids are atoms that accept or take electrons from other compounds, basically meaning that lewis acids usually include, but not limited to metal cations, electron-deficient molecules, or molecules with polar bonds that accept electrons. To put simply, Lewis acids are basically cations.

Lewis bases on the other hand are electron donors, and if Lewis acids tend to be cations, then that means Lewis bases are anions, as in electronegative molecules or molecules with lone pairs, such as NH3. Although the overall charge is 0 for the molecule, NH3 still has the lone pair on the Nitrogen with three bonds to the Hydrogens.

If you want to find out whether a chemical formula is an anion or cation, I suggest that you find the formal charge of the atoms and the overall charge of the molecule!

I really hope that helps because it definitely clarified a lot for me!


thank you!

Earl Garrovillo 2L
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Re: Lewis acids and Bases

Postby Earl Garrovillo 2L » Tue Nov 17, 2020 12:12 pm

Since Lewis acids are electron acceptors and Lewis bases are electron donors, it's best to draw the Lewis dot structure of a compound to see their valence electrons. Compounds that are electron-deficient and need electrons for an octet such as BF3 are bases, while compounds that have lone-pair electrons/cations are likely to be Lewis acids like NH3.

Jenaye Brelland 2I
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Re: Lewis acids and Bases

Postby Jenaye Brelland 2I » Thu Nov 19, 2020 1:56 am

Thank you all for replying! This helped a lot!

Chris_Butler_1A
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Re: Lewis acids and Bases

Postby Chris_Butler_1A » Sun Nov 22, 2020 8:05 pm

I believe in order to distinguish between Lewis Bases and Lewis Acids in a reaction, you need to look at which molecules in the reaction are electron donors and which are electron acceptors. For example, in AlCl4-, which is a reaction between AlCl3 + Cl-, the AlCl3 is the electron acceptor making it the Lewis Acid, while the Cl- is donating an electron which would make it the Lewis Base.

Ethan Goode 2H
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Re: Lewis acids and Bases

Postby Ethan Goode 2H » Sun Nov 22, 2020 8:22 pm

Lewis acids are that when after drawing out the lewis diagram, it is short electrons and could bond to take more electrons from another molecule. The other molecule that gives those two electrons is the lewis base.

David Liu 1E
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Re: Lewis acids and Bases

Postby David Liu 1E » Mon Nov 23, 2020 9:35 pm

lewis acids are compounds/elements that accept electrons, and bases will donate electrons. acids and bases donate/accept in lone pairs, so it's a matter of seeing which ones can donate a lone pair or give one up.


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