We had the task to solve several salts in water and measure the pH value of the solution. After that we should "create" the protolysis equation and to tell about Chemical equilibrium[s].

I get some possible result equations, but I'm really unsure about them. The [] brackets were used to make the ionic loads easier visible. solving equations:

  • $\ce{KNO3 <=> [NO3]- + [K]+}$

  • $\ce{FeCl3 <=> [Fe]^{3+} + [Cl]-}$

  • $\ce{NH4Cl <=> [NH4]+ + [Cl]-}$`

  • $\ce{NaHSO4 <=> [HSO4]- + [Na]+}$

my protolysis equations:

  • $\ce{[NO3]- + H2O <=> HNO3 + [OH]-}$

  • $\ce{[Fe(H2O)6]^{3+} + H2O <=> [Fe(H2O)5OH]^{2+} + [H3O]+}$

  • $\ce{[NH4]+ + H2O <=> NH3 + [H3O]+}$

  • $\ce{[HSO4]- + H2O <=> [SO4]^{2-} + [H3O]+}$

I would say that all equations run bi-directional, because the result of solving equations can vary dependent on temperature for example, and the protolysis equations should be bi-directional because we're having a solution, which isn't a pure acid.

Additionally, I got the question if I can draw conclusions on the pH-change through those protolysis reactions. I would say yes, but not very well, depending on the sum of all hydrogen-containing ions like $\ce{H3O+}$

  • 2
    $\begingroup$ Your equations look balanced and like good equations for representing salt dissolution as well as proton transfer between acid/base species. What's your question exactly? $\endgroup$ – Curt F. Jun 16 '15 at 1:12
  • $\begingroup$ Their directions, and if and how you can draw conclusions about the pH value through the proteolysis equation $\endgroup$ – leAthlon Jun 16 '15 at 3:23

yes, they are, all of them are bidirectional. It is not possible to draw conclusions about the pH value, because of the different abilities to solve in water and because those reaction may cause an increased or a decreased temperature.

(Source: my teacher)

  • 1
    $\begingroup$ This should not be community wiki. Also I believe this is not quite correct. Depending on the involved species, you can predict if a salt will cause a acidic or basic solution based on the involved species. $\endgroup$ – Martin - マーチン Jun 22 '15 at 10:16
  • $\begingroup$ Please change the answer, this question is for my school project not important anymore, so I wanted to lower its priority here too because it won't help that much anymore and I seriously don't want to waste your time for a question which isn't that important $\endgroup$ – leAthlon Jun 22 '15 at 10:20

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