Is it possible to have pure acid? I have a hard trouble understanding this concept. Acids are concentration of H+ and OH- or is the acids the actual acids such as HCl or HI and if one is a strong acid such as HCl can I have pure HCl without water.

You can have pure, anhydrous HCl, but it won't behave as an acid (as HCl is a gas dissolved in water). H2SO4 can be concentrated to 98.6% under standard conditions, and cannot be concentrated further due to disproportionation into sulfur oxides and water. Nitric acid can be concentrated to anhydrous, as far as I know.

 

Acids are proton donors, in that they will donate an H+ to bases, who are proton acceptors (and thus the acid-base reaction).

 

In short, depends on the acid. If it is a gas dissolved in water, such as HCl or HI, likely not: the compound will no longer behave as an acid. If the compound can be a liquid on its own, such as nitric and sulfuric acids, then yes, it can be made anhydrous.

Nitric acid may contain little water but as it gets more concentrated, other N_xO_y compounds appear spontaneously.

 

Phosphoric melts at +42°C, pure one seems to exist. Carboxylic acids?