Question

Pure water at 25°C
ionizes in the presence of acid to form an equilibrium in which
StartBracket upper H subscript 3 upper O superscript plus EndBracket equals StartBracket upper O upper H superscript minus EndBracket equals 10 to the 7 moles per liter.
ionizes in the presence of acid to form an equilibrium in which
StartBracket upper H subscript 3 upper O superscript plus EndBracket equals StartBracket upper O upper H superscript minus EndBracket equals 10 to the negative 7 moles per liter.
self-ionizes to form an equilibrium in which StartBracket upper H subscript 3 upper O superscript plus EndBracket equals StartBracket upper O upper H superscript minus EndBracket equals 10 to the 7 moles per liter.
self-ionizes to form an equilibrium in which
StartBracket upper H subscript 3 upper O superscript plus EndBracket equals StartBracket upper O upper H superscript minus EndBracket equals 10 to the negative 7 moles per liter.

Answer 1

Correct statement: "Pure water at 25°C self‑ionizes to form an equilibrium in which [H3O+] = [OH−] = 10^(−7) mol L−1."

Reason: Kw = [H3O+][OH−] = 1.0×10^(−14) at 25°C. In pure water [H3O+] = [OH−], so each = sqrt(1.0×10^(−14)) = 1.0×10^(−7) M.