What is the molar mass of Mg3(PO4)2, a substance formerly used in medicine as an antacid?

1: 251 g

2: 262.9 g

3: 2.51 g

4: 178.9 g

Answer: 2. 262.9 g

To determine molar mass of a compound, one has to know the molecular masses as well as subscripts or coefficients used in chemical formulas .

The formula given is Mg3(PO4)2.

Molar mass of magnesium (Mg) is 24.3 g/mol.

As the subscript is 3, there are three moles of Mg.

The molar mass of phosphorus (P) is 30.9 g/mol.

Because the subscript is 1, there are 1 mole of P.

The molar mass of oxygen (O) is 16.0 g/mol.

As the subscript is 4, there are 4 moles of O.

The molar mass of the phosphate group (PO4) is:

30. 9 g/mol (P) ×4*16.0g/mol (O)= 94.9 g / mol

Based on the subscript 2, there are two phosphate groups.

Therefore, the molar mass of Mg3(PO4)2 is:

3Mg(24.9 g/mol) * (1 mol of M which is equal to one gram = 262.9 grams should be indicated for the formula of magnesiumphosphat).

Therefore the accurate molar mass is 262.9 g/mol and thus being able to determine molar mass from a given chemical formula is an essential skill in chemistry.