1) Answer is: water molecules.
Balanced chemical reaction: H⁺ + OH⁻ → H₂O.
Neutralization is is reaction in which an acid (for example hydrochloric acid HCl) and a base (for example sodium hydroxide) react quantitatively with each other. In this reaction water and salt are products of reaction.
2) Answer is: 1 x 10⁻⁷.
Water dissociates (autoionization) to form hydrogen ions (H⁺) and hydroxide (OH⁻) ions. The protons (H⁺) hydrate as hydroxonium ions (H₃O⁺).
The Kw (the ionic product for water) at 25°C is 1·10⁻¹⁴ mol²/dm⁶ or 1·10⁻¹⁴ M². Concentration of hydrogen ions and hydroxide ions in pure water are the same.
Kw = [H⁺] · [OH⁻].
[H⁺] = [OH⁻] = 1·10⁻¹⁴ mol²/dm⁶.
3) Answer is: remains constant regardless of the pH.
For example, the Kw (the ionic product for water) at 0°C is 0,12·10⁻¹⁴ mol²/dm⁶ and the Kw (the ionic product for water) at 25°C is 1·10⁻¹⁴ mol²/dm⁶.
The ion product of water only varies with different temperature.
