Predicting Reactants and Products in Replacement Equations

If you are told the reactants and products of a reaction, it is not too difficult to write a balanced chemical equation for the process. But what if you are given only the reactants or only the products, or some combination of the two. Could you write the balanced equation It sounds like a difficult thing to do, but if you know the type of reaction and some or most of the reactants and products, it s likely you can complete the equation. You might want to consult the tables of ions and formula writing in Chapter 4 if you need to brush up on these topics. The focus here is on single- and double-replacement equations. 

Four incomplete equations for single-replacement reactions follow. Each equation has one or more blanks and needs to be completed with the correct species and balanced. 

The first category of single-replacement reactions is one metal replacing another in a compound. Aluminum must replace nickel in NiCl2 to produce nickel metal, Nifo), and aluminum chloride (Al3+ + Cl = AlCl3). Place the formula for aluminum chloride and the symbol for nickel metal in the blanks, and balance. The completed equation is  

You might not know the physical state of some compounds, whether they are solids, liquids, or gases or in solution, but the more important task here is determining the correct formulas for the missing species. Reviewing the three categories of single-replacement reactions shows that most of them occur in solution. 

This equation has a missing reactant and a missing product. This reaction represents the third category of single-replacement reactions. 

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If you answered incorrectly, review Predicting Reactants and Products in Replacement Equations, page 173. 

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