My text says that for an ionic compound like AxBy
if ionic equivalent conductance of Ay+ is a and that of Bx- ion is b,
then the equivalent conductance for AxBy would be a/y + b/x
Now my question is: as the unit of equivalent conductance is S cm2 (gm equivalent)-1 so if i multiply it by a quantity x with unit (gm equivalent) mol-1, then i will get a quantity with unit S cm2 mol-1. This should be the Molar conductance of the ion granted that the value of x was correct. Now for example in Al2(SO4)3 for Al3+ ion the value of x would be 3 because one mole of Al3+ ions would contains 3 gram equivalents. So if equivalent conductance of Al3+ ion was a, then its molar conductance would be 3a and similarly for SO42- ion with equivalent conductance b, the molar conductance would be 2b.
Now from all that i can tell that the molar conductance of Al2(SO4)3 would be,
2(3a) + 3(2b) = 6a + 6b
Now from the formula of equivalent conductance and molar conductance
(Molar conductance)/n = Equivalent conductance
where n is the valence factor for desired compound. So in our case n=6 for Al2(SO4)3
∴ equivalent conductance = (6a + 6b)/6 = a + b
but according to my text it would be a/3 + b/2
Tell me where am i going wrong. And the result I ended up on works for some questions and the thing that my text provided works for some questions, and then there are some questions in which nothing works. I am really confused...
And sorry for any grammatical atrocities.
EDIT: I am just trying to ask that when equivalent conductance of two ions are given to me as a and b, then what would be the equivalent conductance of the compound to which these ions belong? Would it be
a + b
or would it be
a/(charge on first ion) + b/(charge on second ion)
or is it something totally else?