chemistry trouble!

Here I am again :)

Sulfuric acid (H2SO4), a strong acid, is the acid of choice for batteries. The reason a strong acid is used in batteries is because the sulfate in this strong acid (SO4) has relatively less affinity for its hydrogen ion that some of the weaker acids. Giving off the hydrogen ion can form H3O+ and 2 electrons. This is how the charges are stored in a battery. When the battery discharges, the acid is turned into Lead Sulfate and water.

Phosphoric acid (H3PO4), on the other hand, has a strong affinity for its hydrogen. So, it's considered as a weak acid. The phosphorous (PO4) has a strong affinity for its hydrogen, so that makes it unsuitable for use as a battery acid. However, it is useful as a buffer to keep the pH of a solution stable because of its high affinity for hydrogen ions. Remember that high hydrogen ions in a solution makes the solution acidic?