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Balancing Equations by Inspection

Balanced chemical equations have reactants on the left side of the reaction and products on the right side of the equation. The yields arrow is the equivalent of the equals sign in mathematics, but more strict. In chemical equations the yields arrow implies the same number atoms on each side of the equation, the same total mass on each side of the equation, and the same total charge on each side of the equation. Descriptions of the reactants and products are often given as subscripts behind the formulas of the compounds:

(s) = solid, (products may be indicated by a down pointing arrow)
(l) = liquid
(g) = gas, (products may be indicated by an up pointing arrow)
(aq) = aqueous, dissolved in water

Conditions of the reaction may be placed above or below the yields arrow, solvent, reaction temperature, etc. A common symbol found here is often a small triangle (actually representing a small flame) meaning the application of heat.

There is but one way to get good at balancing chemical equations by inspection, an that is to practice at it.

  1. Balance the equations below by inspection:

    1. _____ Ca(s) + _____ O2(g) ---------> _____ CaO(s)

    2. _____ CaSO4(s) + _____ C(s)-----> ____ CaS(s) + _____ CO(g)

    3. _____ C3H8(g) + _____ O2(g) -------> _____ CO2(g) + _____ H2O(g)

    4. _____ P2O5(s) + _____ H2O(l) -------> ______ H3PO4(aq)

    5. _____ Na2O(s) + ______ H2O(l) -----> ______ NaOH(aq)

    6. _____ C4H10(g) + ______ O2(g) ------> _____ CO2(g) + _____ H2O(l)

    7. ___ Mg(OH)2(s) + ___H3PO4(aq) -----> ____ Mg3(PO4)2(s) + ____ H2O(l)

    8. ___ HCl(aq) + ___ Ba(OH)2(aq) ----> ___ BaCl2(aq) + ____ H2O(l)

    9. ____ HgO(s) -----> _____ Hg(l) + _____ O2(g)

    10. __ AgNO3(aq) + __ BaCl2(aq) ---> ___ AgCl(s) + ___ Ba(NO3)2(aq)

    11. _____ H2O2(aq) ------> H2O(l) + O2(g)

    12. _____ C6H12O6(s) -------> _____ C(s) + _____ H2O(g)

    13. ___ HC2H3O2(aq) + ___ NaOH(aq) -----> ___ NaC2H3O2(aq) + ___ H2O(l)