Ionic equations predicting precipitation reactions

In the previous section, we used a precipitation reaction to illustrate how to convert a molecular equation to an ionic equation. A precipitation reaction occurs in aqueous solution because one product is insoluble. A precipitate is an insoluble solid compound formed during a chemical reaction in solution. To predict whethCT a precipitate will form when you mix two solutions of ionic compounds, you need to know whether any of the potential products that might form are insoluble or not This is another application of the solubility rules (Section 4.1). 

Predict the precipitate if any, likely to be formed when aqueous solutions of sodium phosphate, and lead(II) nitrate are mixed. Write the net ionic equation for the reaction. 

Self-Test I.3A Predict the identity of the precipitate that forms, if any, when aqueous solutions of ammonium sulfide and copper(II) sulfate are mixed, and write the net ionic equation for the reaction. 

Predict what will happen when the following pairs of substances are allowed to react. Write a balanced chemical equation for each reaction. When the reaction involves ions, write a net ionic equation. Identify each reaction as precipitation, as acid-base, or as redox, (a) AgN03(a q) and NaCl(a q) (b)... 

PROBLEM 4.6 Predict whether a precipitation reaction will occur in each of the following situations. Write a net ionic equation for each reaction that does occur. 

Some metal salts, such as NaCl, are quite soluble in water, while others, such as AgCl, are not very soluble at all. In fact, so little AgCl dissolves in water that this compound is generally considered to be insoluble. Precipitation reactions occur when certain cations and anions combine to produce an insoluble ionic solid called a precipitate. One laboratory use of precipitation reactions is in identifying the ions present in a solution, as shown in Figure 5-7. In industry, precipitation reactions are used to manufacture numerous chemicals. In the extraction of magnesium mefal from seawater, for instance, the first step is to precipitate Mg " " as Mg(OH)2(s). In this section, the objective is to represent precipitation reactions by chemical equations and to apply some simple rules for predicting precipitation reactions. 

As we saw in Chapter 4, a precipitate forms when a cation from one solution combines with an anion from another solution to form an insoluble ionic solid. We also considered how to predict whether such a reaction would occur and, if so, how to represent it by a net ionic equation. 

Our goal in this chapter is to help you learn about reactions in aqueous solutions, including titrations. We will present a set of solubility rules you can use to predict whether or not precipitation will take place when two solutions are mixed. You may want to talk to your instructor and/or check your text for other solubility rules. These rules will be useful as you learn to write net ionic equations. If you are unsure about mass/mole relationships, you may want to review Chapter 3. And remember—Practice, Practice, Practice. 

In this chapter, you learned about solutions and how to use molarity to express the concentration of solutions. You also learned about electrolytes and nonelectrolytes. Using a set of solubility rules allows you to predict whether or not precipitation will occur if two solutions are mixed. You examined the properties of acids and bases and the neutralization reactions that occur between them. You then learned about redox reactions and how to use an activity table to predict redox reactions. You learned about writing net ionic equations. Finally, you learned how to use the technique of titrations to determine the concentration of an acid or base solution. 

There are three important classes of aqueous reactions. Precipitation reactions occur when solutions of two ionic substances are mixed and a precipitate falls from solution. To predict whether a precipitate will form, you must know the solubility of each potential product. Acid-base neutralization reactions occur when an acid is mixed with a base, yielding water and a salt. The neutralization of a strong acid with a strong base can be written as a net ionic equation, in which nonparticipating, spectator ions are not specified ... 

Infer what the student observed in each test tube. Write a net ionic equation if you predict that a precipitate formed. Write "NR" if you think that no reaction occurred. 

Tip-off You are asked to predict whether a precipitation reaction will take place between two aqueous solutions of ionic compounds, and if the answer is yes, to write the complete equation for the reaction. 

Given formulas for two ionic compounds, predict whether a precipitate will form when water solutions of the two are mixed, and write the complete equation that describes the reaction. (Section 4.2)... 

Aqueous solutions of ionic compounds contain dissolved positive, and negative ions. When two such solutions are mixed, the ions may take part in a double-replacement reaction. One outcome of a double-replacement reaction is the formation of a precipitate. By writing ionic equations and knowing the solubilities of specific ionic compounds, you can predict whether a precipitate will be formed. 

To predict whether a precipitate forms when we mix aqueous solutions of two strong electrolytes, we must (1) note the ions present in the reactants, (2) consider the possible cation-anion combinations, and (3) use Table 4.1 to determine if any of these combinations is insoluble. For example, will a precipitate form when solutions of Mg(N03)2 and NaOH are mixed Both substances are soluble ionic compounds and strong electrolytes. Mixing the solutions first produces a solution containing Mg, N03, Na, and OH ions. Will either cation interact with either anion to form an insoluble compound Knowing from Table 4.1 that Mg(N03)2 and NaOH are both soluble in water, our only possibilities are Mg " with OH and Na with N03. From Table 4.1 we see that hydroxides are generally insoluble. Because Mg " " is not an exception, Mg(OH)2 is insoluble and thus forms a precipitate. NaN03, however, is soluble, so Na" " and NO3 remain in solution. The balanced equation for the precipitation reaction is... 

Predicting Whether a Precipitation Reaction Occurs Writing Ionic Equations... 

Double-Replacement Precipitation Reactions COAL 7 Predict whether a precipitate will form when known solutions are combined if a precipitate forms, write the net ionic equation. (Reference to a solubility table or a solubility rules list may or may not be allowed.)... 

The remaining questions include all types of reactions discussed in this chapter. Use the activity series and solubility guidelines to predict whether redox or precipitation reactions will take place. If a reaction will take place, write the net ionic equation if not,... 

Identify each of these exchange reactions as a precipitation reaction, an acid-base reaction, or a gas-forming reaction. Predict the products of each reaction and write the molecnlar, complete ionic, and net ionic equations. 

Precipitation Reactions—Some reactions in aqueous solution involve the combination of ions to yield a water-insoluble solid—a precipitate. Precipitation reactions are generally represented by net ionic equations, a form in which only the reacting ions and solid precipitates are shown, and spectator ions are deleted. Precipitation reactions usually can be predicted by using a few simple solubility guidelines (Table 5.1). 

When you mix two aqueous ionic compounds together, there are two possible outcomes. Either the compounds will remain in solution without reacting, or one aqueous ionic compound will chemically react with the other. How can you predict which outcome will occur Figure 9.4 shows what happens when an aqueous solution of lead(II) nitrate is added to an aqueous solution of potassium iodide. As you can see, a yellow solid—a precipitate—is forming. This is a double displacement reaction. Recall, from Chapter 4, that a double displacement reaction is a chemical reaction that involves the exchange of ions to form two new compounds. It has the general equation... 

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