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C3 pages 123-126 (the mole (the Avogadro constant (it is such a long…

- - - - in other words one mole of atoms of any substance will have a mass in grams equal to the relative formula mass or relative atomic mass for that substance
      - carbon has a relative atomic mass of 12 so one mole of carbon weighs exactly 12g
      - nitrogen gas (N2) has a relative formula mass of 28 (2x14) so one mole of it weighs exactly 28g
- - - - before the reaction the gas is floating around in the air (its there but its not contained in the reaction vessel so you cant account for its mass)
      - when the gas reacts to form to form part of the product, it becomes contained inside the reaction vessel. therefore the total mass of the stuff inside the reaction vessel increases
      - for example, when a metal reacts with oxygen in an unsealed container, the mass of the container increases. the mass of the metal oxide produced equals the total mass of the metal and the oxygen that reacted from the air
        metal + oxygen --> metal oxide
    - - before the reaction all the reactants are contained in the reaction vessel
      - if the vessel isn't enclosed then the gas can escape from reaction vessel as its formed. because its no longer contained in the reaction vessel you cant account for its mass. therefore the total mass of the stuff inside the reaction vessel decreases
      - for example, when a metal carbonate thermally decomposes to form a metal oxide and carbon dioxide gas, the mass of the reaction vessel will decrease if it isn't sealed. but in reality the mass of the metal oxide and the carbon dioxide produced will equal the mass of the metal carbonate that decomposed.
        metal carbonate --> metal oxide +carbon dioxide
- - - - 2) divide the number of moles of each substance by the smallest number of moles in the reaction
      - 3) if any numbers aren't whole numbers, multiply all the numbers by the same amount so that they all become whole numbers
      - 1) divide the mass of each substance by its relative formula mass to find the number of moles
      - 4)write the balanced symbol equation for the reaction by putting these numbers in front of the chemical formulas