The molar mass of a species is the mass in grams of 1 mole (6.023x10^{23}) of that species, i mole of atoms, 1 mole of molecules or 1 mole of formula units. So it is necessary to calculate the molecular or formula mass of each compound to get its molar mass.

Molar mass is the mass (in grams) of one mole of a substance.Using the atomic mass of an element and multiplying it by the conversion factor grams per mole (g/mol), you can calculate the molar mass of that element.

- One mole of an element is 6.023x10
^{23}atoms of that element. - One mole of an element is an amount of that element equal to its molar mass (an amount equal to its atomic mass in grams).

I mole of any element is an amount equal to its atomic mass in grams, its **molar mass**.

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Solved problems based on molar mass and molecular mass are given below.

### Solved Examples

**Question 1: **Find the molar mass of Ca_{3}(PO_{4})_{2}?

** Solution: **

Determining the formula mass of calcium phosphate Ca_{3}(PO_{4})_{2}, which has 3 calcium ions, Ca^{2+}, and 2 phosphate ions PO_{4}^{2-},
starts by counting the atoms of each element in the formula 3Ca, 2P and
8O and ends by adding the atomic masses of the 13 atoms.

The formula of Ca_{3}(PO_{4})_{2} = 3Ca + 2P + 8O

(3Ca x 40.08amu) + (2P x 30.97amu) + (8O x 16.00amu) = 310.18amu

The formula mass of Ca_{3}(PO_{4})_{2} = 310.18amu

The molar mass of Ca_{3}(PO_{4})_{2} = 310.18g

1 mole of Ca_{3}(PO_{4})_{2} = 310.18g of Ca_{3}(PO_{4})_{2} = 6.023 x 10^{23} formula units

**Question 2: **Find the molar mass of MgSO_{4}.7H_{2}O?

** Solution: **

Hydrates are also ionic compounds that contain a definite amount of water in the crystalline solid.

The hydrate of magnesium sulfate. MgSO_{4}.7H_{2}O has 1 Mg^{2-} ion, 1 SO_{4}^{2-} ion and 7 molecules of water in the formula unit.

Seven moles of water are present for each 1 mole of MgSO_{4}.

There are 27 atoms in the formula unit: 1Mg, 1S, 11O and 14H.

The formula mass of MgSO_{4}.7H_{2}O is

The formula of MgSO_{4}.7H_{2}O = 1Mg + 1S + 11O + 14H

(1Mg x 24.31amu) + (1S x 32.07amu) + (11O x 16.00amu) + (14H x 1.008amu) = 246.49amu

**The molar mass of MgSO**_{4}.7H_{2}O = 246.49g

1 mole of MgSO_{4}.7H_{2}O = 246.49g of MgSO_{4}.7H_{2}O = 6.022 x 10^{23} formula units.

Determining the formula mass of calcium phosphate Ca

The formula of Ca

(3Ca x 40.08amu) + (2P x 30.97amu) + (8O x 16.00amu) = 310.18amu

The formula mass of Ca

The molar mass of Ca

1 mole of Ca

Hydrates are also ionic compounds that contain a definite amount of water in the crystalline solid.

The hydrate of magnesium sulfate. MgSO

Seven moles of water are present for each 1 mole of MgSO

There are 27 atoms in the formula unit: 1Mg, 1S, 11O and 14H.

The formula mass of MgSO

The formula of MgSO

(1Mg x 24.31amu) + (1S x 32.07amu) + (11O x 16.00amu) + (14H x 1.008amu) = 246.49amu

1 mole of MgSO