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Writing and Balancing Equations


    An unbalanced equation can be seen below:

Na + Cl2         --->         NaCl
Reactant(s)                 Product


    When Sodium is added to Chlorine, the result is Sodium Chloride. Remember to add the “-ide” prefix to the end of the second element, because one is a metal (Sodium – NA), and the second is a nonmetal (Chlorine – Cl2).


Balancing the unbalanced equation:

Na + Cl2         --->         NaCl
Reactant(s)                  Product

2Na + Cl2         --->         2NaCl



The Steps:

1.    Write out the unbalanced equation. Ensure that you have copied all of the chemical formulas correctly.
2.    Begin with the most complex substance – the substance with the largest number or greatest variety of atoms. Balance the atoms that occur in the largest numbers. Leave your HO’s (Hydrogen and Oxygen), and all other elements that occur in smaller numbers until later.
3.    Balance any polyatomic ions that occur on both sides of the equation as one unit, rather than as separate atoms.
4.    Balance any Hydrogen or Oxygen atoms that occur in a combined or uncombined state.
5.    Balance any other element that occurs in its uncombined state.
6.    Check your answer by counting the number of atoms on each element on each side of the equation.

Example:

Copper (II) nitrate reacts with Potassium hydroxide to form Potassium nitrate and solid Copper (II) hydroxide. Balance the equation.

Copper: Cu+2     |    Nitrate: NO3-1      --->      Cu(NO3)2

Potassium: K+1    |    Hydroxide: OH-1      --->      KOH


Now that we’ve corrected the chemical formulas, we can continue with the balancing.

Cu(NO3)2  +  KOH      --->      KNO3  +  Cu(OH)2
Cu(NO3)2  +  2KOH      --->      2KNO3  +  Cu(OH)2



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