How would you determine the formula and molar mass of aluminum sulfide?

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Answer 1 · 2016-12-03T21:15:56

#"Aluminum sulfide"# #-=# #Al_2S_3#.

So how did I know?

Aluminum commonly forms an #Al^(3+)# ion.

And sulfur (like congeneric oxygen) commonly forms a #S^(2-)# ion.

To make a neutral salt, the charge must balance hence, #Al_2S_3#.

Note that these ionic identities can be predicted by the position of these elements on the Periodic Table. How?

And as to the masses, sulfur has a mass of #32.06*g*mol^-1#, and aluminum has a mass of #26.98*g*mol^-1#.

And thus the molar mass of #"aluminum sulfide "= (2xx26.98+3xx32.06)*g*mol^-1=??*g*mol^-1#.