18.9 Occurrence, preparation, and compounds of oxygen  (Page 13/27)

FrO ₂

(a) $\text{2Zn}(s)+{\text{O}}_2(g)⟶\text{2ZnO}(s);$ (b) ${\text{ZnCO}}_3(s)⟶\text{ZnO}(s)+{\text{CO}}_2(g);$ (c) ${\text{ZnCO}}_3(s)+2{\text{CH}}_3\text{COOH}(aq)⟶\text{Zn}{({\text{CH}}_3\text{COO})}_2(aq)+{\text{CO}}_2(g)+{\text{H}}_2\text{O}(l);$ (d) $\text{Zn}(s)+\text{2HBr}(aq)⟶{\text{ZnBr}}_2(aq)+{\text{H}}_2(g)$

$\text{Al}{(\text{OH})}_3(s)+3{\text{H}}^{\text{+}}(aq)⟶{\text{Al}}^{\mathrm{3+}}+3{\text{H}}_2\text{O}(l);$ $\text{Al}{(\text{OH})}_3(s)+{\text{OH}}^{-}⟶{\left[\text{Al}{(\text{OH})}_4\right]}^{\text{−}}(aq)$

(a) ${\text{Na}}_2\text{O}(s)+{\text{H}}_2\text{O}(l)⟶\text{2NaOH}(aq);$ (b) ${\text{Cs}}_2{\text{CO}}_3(s)+\text{2HF}(aq)⟶\text{2CsF}(aq)+{\text{CO}}_2(g)+{\text{H}}_2\text{O}(l);$ (c) ${\text{Al}}_2{\text{O}}_3(s)+6{\text{HClO}}_4(aq)⟶\text{2Al}{({\text{ClO}}_4)}_3(aq)+3{\text{H}}_2\text{O}(l);$ (d) ${\text{Na}}_2{\text{CO}}_3(aq)+\text{Ba}{({\text{NO}}_3)}_2(aq)⟶2{\text{NaNO}}_3(aq)+{\text{BaCO}}_3(s);$ (e) ${\text{TiCl}}_4(l)+\text{4Na}(s)⟶\text{Ti}(s)+\text{4NaCl}(s)$

HClO ₄ is the stronger acid because, in a series of oxyacids with similar formulas, the higher the electronegativity of the central atom, the stronger is the attraction of the central atom for the electrons of the oxygen(s). The stronger attraction of the oxygen electron results in a stronger attraction of oxygen for the electrons in the O-H bond, making the hydrogen more easily released. The weaker this bond, the stronger the acid.

As H ₂ SO ₄ and H ₂ SeO ₄ are both oxyacids and their central atoms both have the same oxidation number, the acid strength depends on the relative electronegativity of the central atom. As sulfur is more electronegative than selenium, H ₂ SO ₄ is the stronger acid.