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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: xshadow on January 27, 2019, 04:30:31 AM

Title: Ionic strenght Na2SO4
Post by: xshadow on January 27, 2019, 04:30:31 AM

HI, I know the ionic strenght of Na₂SO₄ 0.0250M is:
μ= 1/2*(0.0500*(+1)² + 0.0250*(-2)²)= 0.0750

But this if I put [SO₄^2-]=2* C_Na2SO4 (no hydrolysis)

But can occur the reaction :
SO₄^2-+ H₂O <------> HSO₄^- + OH^-   pkb


Now  what's the μ expression when I consider the partial dissociation?
Perhaps
μ=1/2*(0.0500*(+1)² + 0.0250*(-2) ²*α_SO42- + 0.0250* (-1)²*α_HSO4^-)
???

Thanks

Title: Re: Ionic strenght Na2SO4
Post by: Borek on January 27, 2019, 12:43:28 PM

You need to find the equilibrium concentrations of all ions involved and use them to calculate ionic strength. It will change the equilibrium so you should then recalculate everything. Typically 2-3 iterations are enough.