01 Introduction to Chemistry
02 Matter and the Atomic Structure
03 The Mole Concept, Chemical Formula and Equation
04 The Periodic Table of Elements
05 Chemical Bond
06 Acids, Bases and Salts
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3.3.3 Percentage of Mass*

Percentage of Composition of a Compound

  1. To find the percentage of composition of a substance means to find the percentage of mass of each element in the molecule of the substance to the mass of the molecule.
  2. The percentage of mass of an element can be determined by the following equation:


    RAM = Relative atomic mass
    RMM = Relative molecular mass

Example

Calculate the percentage of composition of DDT (C14H9Cl5). [Relative atomic mass: Carbon = 14; Hydrogen = 1; Chlorine = 35.5]

Answer: 

Relative molecular mass of DDT
=14(12)+9(1)+5(35.5)
=354.5