1.1 Formulae and equations

  • Created by: zopetre_
  • Created on: 18-01-17 11:08

List of common compounds that are necessary to kno


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List of common ions that are necessary to learn


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What is the definition of oxidation number?

Oxidation number is the number of electrons that need to be added to or taken away from an element to make it neutral.

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What are the rules that apply to oxidation numbers

  • The oxidation number of an uncombined element is 0.
  • The sum of the oxidaton number in a compound is 0.
  • The sum of the oxidation number in an ion equals the overall charge.
  • In compounds the oxidation numbers of Group 1 metals is +1 and Group 2 metals is +2.
  • The oxidation number of oxygen is -2 in compounds (except with fluorine or in peroxides or superoxides)
  • The oxidation number of hydrogen is +1 in compounds (except in metal hydrides)
  • In chemical species with atoms of more than one element, the most electronegative element is given the negative oxidation number.
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What are the steps to balance an equation?

  • Write a word equation for the reaction
  • Write the symbols/formulae for each reactant and product
  • Balance the equation by multiplying the formulae
  • Check your answer
  • Add state symbols
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