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Ch.4 - Reactions in Aqueous Solution
Brown - Chemistry: The Central Science 14th Edition
Brown14th EditionChemistry: The Central ScienceISBN: 9780134414232Not the one you use?Change textbook
All textbooksBrown 14th EditionCh.4 - Reactions in Aqueous SolutionProblem 92b
Chapter 4, Problem 92b

The accompanying photo shows the reaction between a solution of Cd(NO3)2 and one of Na2S. (b) What ions remain in solution?

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Identify the ions present in the reactants: Cd(NO3)2 dissociates into Cd^2+ and NO3^- ions, while Na2S dissociates into Na+ and S^2- ions.
Write the possible products of the reaction by considering the exchange of ions. The potential products are CdS and NaNO3.
Determine the solubility of the potential products. CdS is insoluble in water, so it will precipitate, while NaNO3 is soluble and remains in solution.
Identify the ions that form the soluble product. Since NaNO3 remains in solution, the Na+ and NO3^- ions will be present in the solution.
Conclude which ions remain in solution after the reaction. The ions that remain in solution are Na+ and NO3^-.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Ionic Compounds and Dissociation

Ionic compounds, such as Cd(NO3)2 and Na2S, dissociate into their constituent ions when dissolved in water. This process involves the separation of the positive and negative ions, allowing them to move freely in the solution. Understanding this dissociation is crucial for predicting which ions remain in solution after a reaction.
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Precipitation Reactions

A precipitation reaction occurs when two soluble ionic compounds react to form an insoluble compound, or precipitate. In the case of Cd(NO3)2 and Na2S, the reaction produces cadmium sulfide (CdS), which is insoluble in water. Recognizing the formation of a precipitate helps identify which ions will no longer be present in the solution.
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Spectator Ions

Spectator ions are ions that do not participate in the actual chemical reaction and remain unchanged in the solution. In the reaction between Cd(NO3)2 and Na2S, the sodium ions (Na+) and nitrate ions (NO3-) are spectator ions, as they do not form a precipitate and remain in the solution after the reaction occurs.
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Related Practice
Textbook Question

Antacids are often used to relieve pain and promote healing in the treatment of mild ulcers. Write balanced net ionic equations for the reactions between the aqueous HCl in the stomach and each of the following substances used in various antacids: (a) Al(OH)3(s) (b) Mg(OH)2(s) (c) MgCO3(s) (d) NaAl(CO3)(OH)2(s) (e) CaCO3(s).

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Textbook Question

A 0.5895-g sample of impure magnesium hydroxide is dissolved in 100.0 mL of 0.2050 M HCl solution. The excess acid then needs 19.85 mL of 0.1020 M NaOH for neutralization. Calculate the percentage by mass of magnesium hydroxide in the sample, assuming that it is the only substance reacting with the HCl solution.

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Textbook Question

The commercial production of nitric acid involves the following chemical reactions:

4 NH3(g) + 5 O2(g) → 4 NO(g) + 6 H2O(g)

2 NO(g) + O2(g) → 2 NO2(g)

3 NO2(g) + H2O(l) → 2 HNO3(aq) + NO(g)

(a) Which of these reactions are redox reactions?

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Textbook Question

A 1.248-g sample of limestone rock is pulverized and then treated with 30.00 mL of 1.035 M HCl solution. The excess acid then requires 11.56 mL of 1.010 M NaOH for neutralization. Calculate the percentage by mass of calcium carbonate in the rock, assuming that it is the only substance reacting with the HCl solution.

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Textbook Question

Uranium hexafluoride, UF6, is processed to produce fuel for nuclear reactors and nuclear weapons. UF6 can be produced in a two-step reaction. Solid uranium (IV) oxide, UO2, is first made to react with hydrofluoric acid (HF) solution to form solid UF4 with water as a by-product. UF4 further reacts with fluorine gas to form UF6. (a) Write the balanced molecular equations for the conversion of UO2 into UF4 and the conversion of UF4 to UF6. (b) Which step is an acid-base reaction?

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