strength of an acid

Acidity
Basicity
The Conjugate Seesaw

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rachaeld_1D
Posts: 17
Joined: Fri Sep 26, 2014 2:02 pm

strength of an acid

Postby rachaeld_1D » Mon Dec 08, 2014 11:27 pm

In the book, it says, "the greater the electronegativity of A, the stronger the acid HA."

Why is this the case? I thought that the higher the electronegativity of A, the stronger the bond between H--A; therefore, the weaker the acid. In the course reader it says that HCl is more acidic than HF because the longer the bonds the more acidic it is. Any help is appreciated to help clear my confusion.

Regina Chi 2K
Posts: 51
Joined: Fri Sep 26, 2014 2:02 pm

Re: strength of an acid

Postby Regina Chi 2K » Tue Dec 09, 2014 12:42 am

For binary acids (HA), we must take into account both bond length and the electronegativity of A. Yes, it is true that the longer (more distance) between the bonds of H and A, the easier it is for H to detach from A because there is less attraction (used to compare and contrast A in same vertical groups). However, if we were to compare two elements in the same row, the more electronegative the A is, the more acidic it is. Since the A is more electronegative, it will be pulling more electrons towards it and it will be more polar (more uneven sharing of the electrons) and the H will also then easily detach from the A. Acidity is basically measured by how easily the H can break off of the original molecule (the easier it is, the more acidic it is and vice-versa). I hope this helped!


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