Question

Calculate formula unit mass of Al2[CO3]3,

Answer 1

Carbonate is CO3 with a -2 charge and, Aluminum has a +3 charge
On combining them it would be Al2(CO3)3, meaning that the compound has —
2 total Aluminums
3 total carbons
9 total Oxygen
Now, mass of Aluminum (2×27= 54 amu)
mass of Carbon(3×12 = 36 amu)
And, mass of Oxygen (9×16 = 144 amu)

Therefore, sum of all masses (Al+C+O) = 54+36+144 = 234 amu

Thus, 234 grams exist in 1 Mole of Aluminum Carbonate.

Answer 2

What is formula unit mass ?

- It is similar to molecular mass except for the fact that it is used for the substances whose constituent particles are ions . It is the sum of atomic masses of elements present in a formula unit of a substance .

To find,

Formula unit mass of Al2(CO3)3

Solution :

Here ions are :-

Al 3+

CO3 2-

Formula unit mass = 27×2 + ( 12 + 48 )3

                                  = 54 + 180

                                  = 234u or 234amu