For many equations, as one proceeds through balancing process, coefficients entered previously may need to be adjusted.
Consider unbalanced equation for the thermal decomposition of potassium chlorate to potassium chloride and oxygen gas.
Step 1:
The equation have correct formulae and have the form reactants
products.
KClO3(s) KCl(s) + O2(g)
Step 2:
Compare the number of each type of atom in reactants in products.
Step 3:
Balance the element occurring in the fewest formulae first.
If there is more than one element in this category, choose an element other than oxygen or hydrogen.
No change required above. both K and Cl are balanced
Step 4:
Then balance the next element in the next fewest formulae. Adjust previously entered coefficients if is necessary.
Step 5:
Continue by balancing any remaining atoms.
Good idea to balance elemental forms last! It is in general good practice to leave the balancing of atoms that occur in the elemental form until last because a coefficient entered on an elemental form does not upset the balancing of any other type of atom.
Consider unbalanced equation for the thermal decomposition of potassium chlorate to potassium chloride and oxygen gas.
Step 1:
The equation have correct formulae and have the form reactants
products.KClO3(s)
KCl(s) + O2(g)Compare the number of each type of atom in reactants in products.
1 K 1 Cl and 3 O in reactants 1 K 1 Cl 2 O in products
1 K 1 Cl 2 O in productsStep 3:
Balance the element occurring in the fewest formulae first.
If there is more than one element in this category, choose an element other than oxygen or hydrogen.
No change required above. both K and Cl are balanced
Step 4:
Then balance the next element in the next fewest formulae. Adjust previously entered coefficients if is necessary.
2KClO3(s) 2KCl(s) + 3O2(g)
2KCl(s) + 3O2(g)To balance O,
the coefficient of BOTH oxygen species must be changed.
This 2-3 combination is common!
Then the coefficient of KCl had to be changed.
the coefficient of BOTH oxygen species must be changed.
This 2-3 combination is common!
Then the coefficient of KCl had to be changed.
Step 5:
Continue by balancing any remaining atoms.
No further changes required as the equation is balanced.
2 K 2 Cl and 6 O in reactants 2 K 2 Cl 6 O in products
2 K 2 Cl and 6 O in reactants
2 K 2 Cl 6 O in productsGood idea to balance elemental forms last! It is in general good practice to leave the balancing of atoms that occur in the elemental form until last because a coefficient entered on an elemental form does not upset the balancing of any other type of atom.