a).
HBr + H2O <=> Br(-) + H3O(+)
Ka = [H3O(+)]x[Br(-)]/[HBr]
H2S + H2O <=> HS(-) + H3O(+)... Ka1
Ka1 = [HS(-)]x[H3O(+)]/[H2S]
HS(-) + H2O <=> S(2-) + H3O(+)...Ka2
Ka2 = [S(2-)]x[H3O(+)]/[HS(-)]
unde Ka1 > Ka2
HBr > H2S >> HS(-)
10^9...9,1x10^-8...1,1x10^-12
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sensul scaderii aciditatii