Is the law of composition true for all types of compounds?Mention why or why not?
Answers
No, law of definite proportion is not true for all types of compounds. The law is not valid for non-stoichiometric compounds.These are compounds whose compositions vary from sample to sample.Mainly inorganic compounds come into this class.An example of these types of compound is wustite, which has the formula FeO, but in actual the stoichiometry in this compound is Fe0.95O. This is so because some of the Fe+2 gets easily oxidised to Fe+3 and takes place of Fe+2 in the lattice. To balance the charge 3 Fe+2 atoms are being replaced by 2 Fe+3 atoms. Elements having mixture of stable isotopes also form non-stoichiometric compound. Some of the element position in the crystal structure gets replaced by their isotopes and causes difference in actual composition of the crystal. For example , natural carbon, silicon, and germanium show this type of defect.