Arrhenius acid definition

Definition of an Arrhenius acid
Acids are compounds that can donate H+ ions in water solutions. The role of water is essential in this definition. Pure HF is a gas and is not considered to be an acid. It must be dissolved in water to act like an acid. There are many different acids, but they have something in common. They all have hydrogen attached to a nonmetal from either group 6A or group 7A. This last idea makes it easier to identify acids.
The process in which water accepts a proton from an acid can be viewed as a TUG of WAR between the acid and water. An acid will release a proton to a water molecule. The proton will be covalently bonded to the "O" in water through a covalent bond. The unshared electron pair on the "O" has a strong attract for the proton than the Cl1- ion hydrochloric acid.
proton transfer animation
Binary acids are acids that have hydrogen combined with an atom from either group 7A or 6A. The examples of binary acids are:
HF, HCl, HBr, HI, H2S and H2O.
It may be difficult to picture water as an acid but under certain conditions the water molecule breaks up to form H+ ions and OH- ions. This is one of nature's tricks. Pure water is not typically considered very acidic, because an OH- ions is released along with every H+ ion.
A hydrogen must be covalently bonded to O, S, F, Cl, Br, or I in order to be acidic. This requirement must be met. Any other combination of H and nonmetal element will generally not be weak enough to be broken and form protons in water.
Exercise: Which of the following is an acid? Click here for answer or click on any formula





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Dr. Walt Volland all rights reserved 1997-2005 revised May 2, 2005