Oxoacid strengths in aqueous solutions

In summary, the strength of an acid is determined by its ability to donate a proton, and this is affected by the polarized and strength of its O-H bond. Acids with more oxygen atoms have weaker and more polarized O-H bonds, making it easier for the proton to be released and increasing the acid strength. This is why H2SO4 is a stronger acid than H2SO3, even though they both have the same number of O-H groups.
  • #1
Mangoes
96
1
Hey there,

My textbook doesn't expand on this much and I'm unsure if I'm just not seeing some obvious connection; I'd appreciate it if someone could clarify this for me.

I'm studying the Bronsted-Lowry theory and the strength of binary and ternary acids. I understand how, for example, H2SO4 dissociates in water, but I don't see why the dissociation of that would be any different than say, H2SO3.

I realize that for some reason, acid strength increases with an increased number of oxygen atoms, but I can't understand why.

From what I understand, the O-H bonds are broken in water to create an anion and H+, so why would a larger amount of oxygen atoms in a molecule have anything to do with acid strength since the amount of O-H groups remain constant in both molecules (for example, H2SO4 and H2SO3 both have the same amount of O-H groups.)

What am I misunderstanding or missing?
 
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  • #2


Hello there,

Thank you for reaching out with your question about the Bronsted-Lowry theory and acid strength. It is great that you are trying to understand the concept better and I am happy to clarify it for you.

Firstly, it is important to understand that the strength of an acid is determined by its ability to donate a proton (H+) in an aqueous solution. The more easily an acid can donate a proton, the stronger it is considered to be.

Now, let's look at the specific example you mentioned with H2SO4 and H2SO3. Both of these molecules have the same number of O-H bonds, but the difference lies in the strength of the bonds. In H2SO4, the sulfur atom is bonded to four oxygen atoms, which leads to a more polarized and weaker O-H bond. This makes it easier for the proton to be released, thus making H2SO4 a strong acid. On the other hand, in H2SO3, the sulfur atom is bonded to only three oxygen atoms, resulting in a stronger and less polarized O-H bond. This makes it more difficult for the proton to be released, making H2SO3 a weaker acid.

In general, the more oxygen atoms an acid has, the more polarized and weaker the O-H bond becomes, making it easier for the proton to be released and increasing the acid strength. This is why acids with more oxygen atoms, such as H2SO4, are stronger than those with fewer oxygen atoms, like H2SO3.

I hope this explanation helps to clarify the concept for you. If you have any further questions, please don't hesitate to ask. Keep up the good work in your studies!
 

1. What is an oxoacid?

An oxoacid is a type of acid that contains at least one oxygen atom bonded to a hydrogen atom, along with at least one other non-metallic element. Examples of oxoacids include sulfuric acid (H2SO4) and nitric acid (HNO3).

2. How are oxoacids classified?

Oxoacids are classified based on the number of oxygen atoms bonded to the central atom. For example, if an oxoacid contains one oxygen atom bonded to the central atom, it is classified as a monoprotic acid. If it contains two oxygen atoms, it is classified as a diprotic acid, and so on.

3. What is the relationship between the strength of an oxoacid and the number of oxygen atoms?

In general, the more oxygen atoms an oxoacid has, the stronger it is. This is because the presence of more oxygen atoms allows for more efficient delocalization of the negative charge, making the acid more stable and therefore stronger.

4. How does the strength of an oxoacid change in aqueous solutions?

The strength of an oxoacid can change in aqueous solutions due to the presence of water molecules. Water molecules can act as either a proton donor or a proton acceptor, altering the acidity of the solution. In general, the stronger the acid, the more it will dissociate in aqueous solution, resulting in a lower pH.

5. What factors can affect the strength of an oxoacid in aqueous solutions?

Several factors can affect the strength of an oxoacid in aqueous solutions, including the number of oxygen atoms, the electronegativity of the central atom, and the presence of other functional groups. Additionally, temperature and concentration can also impact the strength of an oxoacid in aqueous solutions.

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