It took half a century to get NH4OH out of our high school and college chemistry textbooks. Arrhenius hypothesized its existence around the turn of the century because ammonia dissolves in water to form a basic solution, and his definition of a base required it to contain an OH group. Diligent research in the 1920s and 1930s failed to provide evidence for it, Lewis structures suggested it was impossible, but it was in our textbooks up to the late 1970s. That’s not the only error in chemistry textbooks. A 0.5M solution of MgCl2 does not contain 0.5M Mg2+. Using published equilibrium constants (Smith RM Martell AE, Critical Stability Constants, vol. 1-4, Plenum, 1975-1982), 36 percent of the Mg exists as MgCl+. Yet introductory high school and college texts encourage students to believe that metal salts are totally ionized in solution! CdCl2 in 1.4M solution exists as 34 percent unionized...

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