F.4 chem--acid

先答(b)

b) 2HnX + 3Mg --> Mg3X2 + nH2

a)

Since Mg3X2 is a normal salt (as it does not contain mobile H ions),
so the basicity of the acid is n.

However, since Mg3X2 is an ionic compound,

the charge of a single ion x is [(+2)*3/2]*-1= -3

And as HnX ionizes in water to form an acid

and X ion carries a charge of -3

So n = 3


Note: An example of the acid in the question will be phosphoric acid

H3(PO4)

(3 and 4 are subscripts)


Hope I can help you!!!!