Molar Mass Formula and Molar Mass Sums

Molar Mass Formula :

Molar mass(kg/ mol) in kilogram per mole is equal to the product of the  mass(g) in gram is divided by mole. Hence the molar mass formula has been written as,

Molar mass(kg/ mol) = mass(g) /  mole

= g/mol

Units of Molar Mass: SI unit is kg/ mol or gm/mol.

Sample Problems :

Example 1:

What is the molar mass of Sodium Carbonate?

Solution :

The chemical formula of Sodium Carbonate is Na2CO3. It contains two sodium atoms, one carbon atom and three oxygen atoms.

We know that the molecular weight of Sodium (Na) is 22.98g/mol, Carbon (C) is 12.011 g/mol and Oxygen (O) is 16 g/mol.

Therefore, the molar mas of sodium carbonate is

Na = 2 * 22.98

= 45.96 g/mol.

C   = 1 * 12.011

= 12.011 g/mol.

O   = 3 * 16

= 48 g/mol.

By adding all we get

= 45.96 + 12.011 + 48

= 105.971

Therefore, the molar mass of Na2CO3 is 105.971 g/mol.

Example 2:

What is the molar mass of Hydrochloric Acid?

Solution :

The chemical formula of Hydrochloric acid is HCl. It contains one Hydrogen atom, one chlorine atom.

We know that the molecular weight of Hydrogen (H) is 1.0078g/mol, Chlorine (Cl) is 35.453 g/mol.

Therefore, the molar mas of hydrochloric acid is

H = 1 * 1.0078

= 1.0078 g/mol.

Cl = 1 * 35.453

= 35.453g/mol.

By adding all we get

= 1.0078 + 35.543

= 36.460 g/mol.

Therefore, the molar mass of HCl is 36.460 g/mol.

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