The molecular weight (or more formally molar mass) of a compound is the sum of all the molar masses, in atomic
mass units, of the elements in the compound. To calculate the molecular weight, the correct formula of the
compound and the molar masses of each atom must be accurately known.
This program is mainly a time-saving utility for calculating molecular weights and percent composition, which is
defined as the percent by mass of each element present in the compound. It is important to note that the
process of calculating molecular weight and percent composition is one in which all people trained in any aspect
of chemistry must be proficient.
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INSTRUCTIONS
Enter the molecular formula of interest in the text box at
the top of the screen.
Enter the formula using the following
syntax for specifying chemical formulae.
A subscripted number or symbol requires an underscrore (
_ ) on both sides of it. For example, H2O would be
entered as H_2_O. Note the underscores on both side of the subscript
'2'.
Entire element groups (such as OH, NO3 etc.) may
be attached a subscript provided the element group is enclosed
in brackets such as these: ( ). For example, Ca(OH)2
would be specified as Ca(OH)_2_.
Waters of hydration or solvents of solvation should also
be written in parenthetical notation. For example, CuSO4
* 5H2O should be entered as CuSO_4_(H_2_O)_5_. Note
the subscript 5 attached to the entire H2O molecule.
Also note that the subscript '4' is attached to only the oxygen
atom of the copper sulphate molecule.
No spaces are allowed at any place within a chemical formula
entered in this syntax.
To calculate the formula weight and percent composition,
click on the Calculate button.