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InterviewSolution
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An aqueous solution contains `10%` amonia by mass and has a density of `0.99 g cm^(-3)`. Calculate hydroxy`1` and hydrogen ion concentration in this solution `K_(a)` for `NH_(4)^(o+) = 5.0 xx 10^(-10)M`. |
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Answer» Given, `("Weight of" NH_(3))/("Weight of solution") = 10//100` `100g` solution contains `10gm NH_(3)` `M_(NH_(3)) = (10 xx 1000) (17 xx (100//0.99)]` `= 5.82(V = mass//density)` Now `{:(NH_(3)+H_(2)Orarr,NH_(4)OHhArr,NH_(4)^(o+)+,overset(Θ)OH,),("Before dissociation",1,0,0,),("After dessociation",(1-alpha),alpha,alpha,):}` `:. [overset(Θ)OH] = Calpha = C sqrt((K_(b)//C)) = sqrt((K_(b)C))` `[C = 5.82M` and `K_(b) = K_(w)//K_(a) = 10^(-14)//(5xx10^(-10)) = 2 xx 10^(-5))` `[overset(Θ)OH] = sqrt(2xx10^(-5) xx 5.82) = 1.07 xx 10^(-2)M` `:. [H^(o+)] = 10^(-14)//1.07 xx 10^(-2) = 0.9268 xx 10^(-12)M` `:. pH =- log [H^(o+)] =- log 0.9268 xx 10^(-12)M = 12.033` |
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