Question

Which of these statements best explains why pure water has a pH of 7?
1) Pure water contains only H20 molecules, but pH is based on the concentration of H30+ ions.
2)Each molecule of water can dissociate to form 7 H30+ ions.
3) water self-ionizes to form an equilibrium system that has [H30+]=1.0x10^-7M

Answer 1

water self-ionizes to form an equilibrium system that has [h30+]=1.0*10^-7M

Your answer is C

Answer 2

A neutral solution would have a pH of 7, which means that the acid and base concentrations are equal. For the case of water, the concentrations of H3O+ and OH- are equal, which is 1.0 x 10^-7 M. Thus, the 3rd statement best explains the neutral pH of water.