Composition of a Ternary Compound - Part 5, Percent Mass Composition for Compounds Containing Polyatomic Ions

Greetings,

This post will cover the determination of element mass percent of a polyatomic-ion-containing compound from the molecular formula.  The case of two or more polyatomic ions in the formula is discussed.  Many compounds of this type contain oxypolyatomic ions such as Nitrate ion and Sulfate ion.

Proper Accounting of Compound Subscripts

The main thing to look out for, in determining molar masses, is to properly account for subscripts inside and outside of parentheses.  The outer subscript must be multiplied by the inner subscripts when calculating molar masses of elements with symbols contained within parentheses.  The following drawing describes the process for a hypothetical general compound.

 

 

Each "% Element" calculation is color-coded to match the symbols used to represent molar mass quantities.  Note that the calculations for % Elements B and C include the outer subscript, "d".

That's all for now.  Have a good one!

A Publication of http://ExcellenceInLearning.biz