Question

What is the molar mass of aluminum sulfate?

Answer 1

Solution
1. The formula unit for aluminum sulfate is Al2(SO4)3.
2. There are 2 atoms of Al, 3 atoms of S and 43 = 12 atoms of O in one formula unit.
3. Find atomic masses of Al, S and O in the periodic table:
Ar(Al) =26.98;
Ar(S) = 32.07;
Ar(O) = 16.00.
4. Find molecular mass of one formula unit of Al2(SO4)3
Mr(Al2(SO4)3) =Ar(Al)2 +Ar(S)3 +Ar(O)12 = 26.982+32.073+16.0012 = 342.17
5. Molar mass and molecular mass have the same magnitude, but molar mass has
dimension – g/mol.
M(Al2(SO4)3) = 342.17 g/mol.
Answer: 342.17g/mol