Question

What is the molar mass and the mass of 5.0 mol of iron(II) phosphate, `Fe_3(PO_4)_2`?

Answer 1

Molar mass: `357.49 gmol^-1`
Mass: `1787.45g`

Explanation:

Molar mass: Add up the individual molar masses of each species

`3(55.85) + 2(30.97 + (4(16.00) ) = 357.49` `gmol^-1`

Mass: Mass = molar mass x number of moles

`357.49` x `5.0 = 1787.45g`

Answer 2

`358 g//mol; 1790g`

Explanation:

the molar mass of a substance is the mass in grams that a mole of atoms - `6.02 * 10^23` atoms - has.

for example, the mass of a mole of carbon is `12g`.

this number, `12`, is the same as the atomic mass displayed on the top-left square for each element in the Periodic Table.

the atomic masses of the Periodic Table can therefore show the molar mass of an element, in grams per mole of atoms.

the atomic mass of iron `Fe` is `56`.

the formula mass (molar mass of a compound) of `Fe_3` is `3 * 56`, which is `168`.

the atomic mass of phosphorus `P` is `31`.

the atomic mass of oxygen `O` is `16`.
the formula mass of `O_4` is `16 * 4`, which is `64`.

the formula mass of `PO_4` is `31 + 64`, which is `95`.
the formula mass of `(PO_4)_2` is `95 * 2`, which is `190`.

the formula mass of `Fe_3(PO_4)_2` is `168 + 190`, which is `358`.

the molar mass of `Fe(SO_4)_2`, in grams per mole, is `358 g//mol`.

if the molar mass of `Fe(SO_4)_2`, is `358 g//mol`. then there are `358g` in one mole of iron phosphate.

in `5` moles of iron phosphate, there are `358 * 5 g`, which is `1790g`.