help with dissociating (1 Viewer)

[sssona09]

so apparently for sulphuric acid it dissociates two times and first its:
H2SO4 + H2O → H3O+ + HSO4-

HSO4- + H2O H3O+ + SO4 2- but the equilibrium is to the left.



and the overall reaction is:H2SO4 + 2H2O → HSO4- + 2H3O+ + SO4 2-
how do they get this overall reaction??

thank you <3

 

[captainhelium]

Correct me if I'm wrong but I think the overall equation doesn't have HSO₄^-. I think the equation should be

H₂SO₄ + 2H₂O 2H₃O⁺ + SO₄^2-

It's basically like simultaneous equations in maths - just add the two equations together. The mono-directional arrow and equilibrium arrow are kind of like your 'equal signs' when adding two simultaneous equations. Also there is one HSO₄^- on the RHS of the top equation and one HSO₄^- on the LHS of the bottom equation so they can cancel out just like in maths.

So when you add the LHS of the two equations, you get two water molecules and one H₂SO₄. Hence you get H₂SO₄ + 2H₂O.

Similarly when you simultaneously add the RHS of the two reactions you get two hydronium ions, and one sulfate ion so you get 2H₃O⁺ + SO₄^2-.

Therefore, the overall equation is

H₂SO₄ + 2H₂O 2H₃O⁺ + SO₄^2-

Hope that helped!

 

[ichila101]

Captain Helium's post is correct with the exception that the overall should have a single arrow not an equilibrium arrow

 

[Powereaper]

The overall doesn't need to have a single arrow, but you can do so. This is because sulfuric acid doesn't completely ionise into sulfate ions. It only dissociates completely for the first ionisation into HSO4- ions, but ionises into sulfate ions in the second ionisation up to around 90ish%.