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    Ok.. so to start with, define the term Kw.. all I could find was its an equilibrium constant?

    1) calculate the pH of water at 50 oC. Explain why pure water at 50 oC is still neutral even it's pH is not 7.

    calculation -

    explanation -


    Don't get this at all...

    2) At 25 oC, Kw has the value 1.00 x10-14.mol2dm-6. calculate the pH at 25 oC of
    i)0.150moldm-3 solution of sodium hydroxide.

    ii) the solution formed when 35.0cm3 of this solution of NaOH is mixed with 40.0cm3 of a 0.120moldm-3 solution of HCl.


    3) In a 0.150moldm-3 solution of a weak acid, HX at 25 oC, 1.80% of the acid molecules are dissociated into ions.

    i) write an expression for Ka for the acid HX.

    ii) Calculate the value of Ka for the acid HX at this temp and state its units.
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    For a start Kw is the equilibrium constant for water
    2H2O -> H3O+ + OH-
    This is temperature dependant. Kw is different at 50C because more dissociates, this affects the H+ concentration since it effectively splits into H+ and OH- and pH is a measure of H+ concentration
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    (Original post by bex_1_2_1)
    Ok.. so to start with, define the term Kw.. all I could find was its an equilibrium constant?

    1) calculate the pH of water at 50 oC. Explain why pure water at 50 oC is still neutral even it's pH is not 7.

    calculation -

    explanation -


    Don't get this at all...

    2) At 25 oC, Kw has the value 1.00 x10-14.mol2dm-6. calculate the pH at 25 oC of
    i)0.150moldm-3 solution of sodium hydroxide.

    ii) the solution formed when 35.0cm3 of this solution of NaOH is mixed with 40.0cm3 of a 0.120moldm-3 solution of HCl.


    3) In a 0.150moldm-3 solution of a weak acid, HX at 25 oC, 1.80% of the acid molecules are dissociated into ions.

    i) write an expression for Ka for the acid HX.

    ii) Calculate the value of Ka for the acid HX at this temp and state its units.
    It is not possible to calculate the pH at 50ºC without further information.

    It is true that:

    kw = [H+][OH-]

    and that kw = 1 x 10-14 @ 25ºC

    BUT without knowing exactly how changing the temperature affects the dissociation quantitatively there is no way to calculate the new pH...
 
 
 
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