Question

How many formula units of aluminum are required to produce 9.9 grams of hydrogen in `2Al + 3H_2SO_4 -> Al_2(SO_4)_3 + 3H_2`?

Answer 1

You have the balanced chemical equation. `"Moles of dihydrogen = "3/2xx"moles of aluminum"`

Explanation:

Given the stoichiometric equation, you have established the stoichiometry.

`"Moles of dihydrogen"` `=` `(9.9*g)/(2.0*g*mol^-1)` `=` `??*mol`.

The moles of aluminum metal is `2/3` this quantity.

And of course `"1 mole"` `=` `6.022xx10^23" formula units"`.