CHEMISTRY · Single correct · A Level · Chemistry · Acids and bases · Acids and bases
Problem
Hydrofluoric acid, HF(aq), is a weak electrolyte whose percent ionization increases as temperature rises. A student prepares a 0.10 mol L⁻¹ HF solution at 25 °C, then warms an identical sample of the same solution to 60 °C. Each option below describes the contents of two same-size boxes—one representing the solution before warming (left) and one after warming (right). In every box there are 90 water molecules. Which option most consistently represents the effect of the temperature change?
(a) Left: 8 HF molecules and 2 H₃O⁺ ions with 2 F⁻ ions; Right: 8 HF molecules and 2 H₃O⁺ ions with 2 F⁻ ions.
(b) Left: 8 HF molecules and 2 H₃O⁺ ions with 2 F⁻ ions; Right: 6 HF molecules and 4 H₃O⁺ ions with 4 F⁻ ions.
(c) Left: 6 HF molecules and 4 H₃O⁺ ions with 4 F⁻ ions; Right: 8 HF molecules and 2 H₃O⁺ ions with 2 F⁻ ions.
(d) Left: 8 HF molecules and 2 H₃O⁺ ions with 2 F⁻ ions; Right: 0 HF molecules and 10 H₃O⁺ ions with 10 F⁻ ions.