How do acids and bases work

Question

i know what pH is and i know how it's measured....what i'm curious is how it works in the molecular level!...what's an H ion and a H3O ion...how does water dissociate to form these....and how would metals react with these, because from experimenting i learned metals dissolve better with a pH that's not 7....but i'm really confused as to why

Answer 1

Personally I found the best way to envision it was to imagine a tetrahedron (four sided shape with equilateral triangles on each face). Consider this shape to be the oxygen atom.

The outer shell is most stable with 8 electrons, arranged in 4 pairs. Oxygen has only 6 electrons in the outer shell, so two of the points of the tetrahedron will have a pair of electrons, while the leftover single electrons are located at the other points. Hydrogen has one electron and one proton, and most stable with 2 electrons in the outer shell (1 pair). When an oxygen and hydrogen molecule collide, they use one of the other's electrons to create a stable pair, resulting in two electrons in the outer shell of the hydrogen, and, when a second hydrogen collides, the oxygen gets 4 pairs of electrons. Thus, H2O is fairly stable.

Now turn the tetrahedron, how with two points connected to hydrogens, so that the hydrogens are at the bottom and the other points at the top. The edge at the top is furthest from the hydrogen proton and hence it has a slightly negative charge (due to the two electron pairs nearby), while the edge at the bottom has a slightly positive charge (in comparison). Hence the water molecule is known as polar.

Imagine a second water molecule (tetrahedron) approaching hydrogen first towards the top edge (between the two electron pairs). As the proton of the hydrogen nears these pairs the force of attraction is slightly stronger from the two electron pairs than from that produced by it's oxygen atom (due to the proximity of the second hydrogen proton).

As a result the proton is pulled off the water molecule producing H3O+ and OH-. Now the inital tetrahedron has three proton "points" and one electron pair point, and the other tetrahedron has one proton point and three electron pair points. When a H3O+ collides with another OH-, same or different ones, the proton is strongly attracted to the large electron field of the OH-, resulting in the proton moving over to the OH-, resulting in two water molecules again.

This back and forth constantly occurs as each molecule is continously colliding with other molecules. When the number of H3O+ and OH- are equal, the pH is 7. If there are more H3O+, then the pH <7, similarly when the OH- is in greater numbers, the pH >7.

Metals

Metals have a low number of electrons in the outermost shell, and are capable of losing electrons ot create a positive ion (eg Mg2+, Na+)

As these positive ions are attracted to the large negative region around OH-, they combine to form compounds (eg Mg(OH)2, NaOH). The more OH- available to collide into, the faster the reaction occurs, thus the higher the pH (the more OH- molecules), the faster the reaction. Similarly if the solution is acidic, the metal is competing with H3O+ for any available OH- molecules and thus the reaction is slower (remember that water is constantly becoming H3O+ and OH- and back again, so even in a solution of H3O+ there still is OH-.)

Answer 2

http://chemistry.about.com/od/acidsbases...

go there its pretty good. nothing beats an old text book though.

Nothing happens when there is a ph of 7 as 7 is neutral.

An H ion is an hydrogen atom that has been charged i think and h3o is three hydrogens attached to one Oxygen.

its been years since i did chemistry but yeah check out a text book at the library. they have the basics of understanding then go more in depth