?Fundamentals of ChemistryDOE-HDBK-1015/1-93CHEMICAL EQUATIONSRev. 0CH-01Page 41Example:Explain the following chemical equation.Solution:This chemical equation shows that iron reacts with water to form ferric oxide andhydrogen gas (the vertical arrow ?indicates a gas). This chemical equation also showsthat for every two atoms of iron that react, three molecules of water are used to formone molecule of ferric oxide and three molecules of hydrogen gas. This is a balancedchemical equation. There are two iron atoms on each side of the equation; there are sixhydrogen atoms on each side; and there are three oxygen atoms on each side.There are no fixed rules for balancing chemical equations. Learning how is a matter of practice.The balancing of most equations can be accomplished by following the guidelines explainedbelow.Guidelines:a.Once the correct chemical formula for a compound is written in an equation, donot modify it.b.Select the compound with the greatest number of atoms. Then begin by balancingthe element in that compound with the most atoms. There must be the samenumber of atoms of an element on each side of the equation. As a rule of thumb,this first element should not be hydrogen, oxygen, or a polyatomic ion.c.Balance the atoms of each element in the compound by placing the appropriatecoefficient in front of the chemical symbol or formula.d.Next, balance the polyatomic ions. In some cases, the coefficient assigned inguideline 2 may have to be changed to balance the polyatomic ion.e.Balance the hydrogen atoms next, then the oxygen atoms. If these elementsappear in the polyatomic ion it should not be necessary to balance them again.f.All coefficients will be whole numbers. The coefficients should be reduced to thelowest possible ratios.g.As simple as it sounds, check off each element as it is accounted for since thiswill prevent double inclusion or a missed atom.
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