Chemical Formulae

Chemical formulae are used as shorthand to indicate how many atoms of one element combine with another element to form a compound.

C₂H₆, 2 atoms of carbon combine with 6 atoms of hydrogen to form ethane.

Na₂Cr₂O₇, two Na combine with 2 Cr and 7 O to form sodium dichromate.

If the formula of a compound is known determining the molar mass is simple. Since we know the atomic masses we can sum the atomic masses to obtain the molecular mass of any molecule.

We also know that 1 mole of C atoms weighs 12.01 g so we know the molar or mass of ethane also.

Or, 30.07 g in 1 mole C₂H₆. So, we say the molar mass of ethane is 30.07 g/mol (that's grams per mole).

Determine the molar mass of Na₂Cr₂O₇

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