Question

A 1.85 mole sample of the ionic compound Al2(SO4)3 contains how many moles of the following? A) Al atoms B) S atoms C) Al3^+

Answer 1

(a) `3.70` `"mol Al"`

(b) `5.55` `"mol S"`

(c) `3.70` `"mol Al"^(3+)`

Explanation:

We're asked to find the number of moles of some species in `1.85` `"mol Al"_2"(SO"_4")"_3`.

(a)

The moles of `"Al"` atoms:

There are `2` atoms of `"Al"` per unit of `"Al"_2"(SO"_4")"_3`, so there are two moles of `"Al"` per mole of `"Al"_2"(SO"_4")"_3`:

`1.85cancel("mol Al"_2"(SO"_4")"_3)((2color(white)(l)"mol Al")/(1cancel("mol Al"_2"(SO"_4")"_3))) = 3.70` `"mol Al"`

(b)

The moles of `"S"` atoms:

There are `3` atoms of `"S"` per units of `"Al"_2"(SO"_4")"_3`, so there are `3` moles of `"S"` per mole** of `"Al"_2"(SO"_4")"_3`:

`1.85cancel("mol Al"_2"(SO"_4")"_3)((3color(white)(l)"mol S")/(1cancel("mol Al"_2"(SO"_4")"_3))) = 5.55` `"mol S"`

(c)

The moles of `"Al"^(3+)` ions:

The number of ions of `"Al"^(3+)` will be the same as the number of atoms of `"Al"`, so the answer will be the same as that for (a) (assuming I understand the question correctly).