Is distill water a acid or a base?

Answer 1

In general it is said to be neutral, but having said so you can (and Mr. Lewis did in his theory on acid and base) see water as both an acid and as base:

• Acid behaviour of H2O, donating a proton to base B-

  H2O + B- --> OH- + HB (1)

• base behaviour of H2O, accepting a proton from acid HB

  H2O + HB --> H3O+ + B- (2)

• Ampholyte*) behaviour: donating a proton to itself as acceptor

  (H2O)donor + (H2O)acceptor <--> OH- + H3O+

  which makes water having both concentrations [H3O+] = [OH-] = 1.0*10-7, so: pH = 7

*) Ampholyt means: both donor and acceptor, at the same time, 'like twins'