Which of the following statements is not true regarding acids? Arrhenius acid is any substance that increases the concentration of hydronium ions. Brønsted-Lowry acid is any substance that donates a hydrogen ion. Lewis acid is a substance that donates a lone-pair of electrons. The pH is less than 7.0.

Question

Which of the following statements is not true regarding acids?  Arrhenius acid is any substance that increases the concentration of hydronium ions.  Brønsted-Lowry acid is any substance that donates a hydrogen ion.  Lewis acid is a substance that donates a lone-pair of electrons.  The pH is less than 7.0.

anonymous · Answer

Well, they all have problems.  An Arrhenius acid is one that increases the concentration of H+ BY DISSOCIATING,  a Bronsted-Lowry acid is one that donates an H+ TO WATER, a Lewis acid is one that can ACCEPT a lone pair, and the pH of an acid solution is less than 7 only at about 25oC.

However, three of four of those are minor points.  The most egregiously wrong statement is that a Lewis acid donates instead of accepts a lone pair.  This should be obvious because you know H+ itself is an acid, and obviously it has no lone pair to donate.