Question

Using the general solubility rules given in Table \(6-1,\) name three reagents that would form precipitates with each of the following ions in aqueous solution. Write the net ionic equation for each of your suggestions. a. chloride ion d. sulfate ion b. calcium ion e. mercury(I) ion, \(\mathrm{Hg}_{2}^{2+}\) c. iron(III) ion f. silver ion

Short answer

For chloride ions, precipitates can form with silver nitrate, lead nitrate, and mercury(II) nitrate. The net ionic equations are: 1. \(Ag^+ + Cl^- \rightarrow AgCl\) 2. \(Pb^{2+} + 2Cl^- \rightarrow PbCl_2\) 3. \(Hg^{2+} + 2Cl^- \rightarrow HgCl_2\) For sulfate ions, precipitates can form with barium chloride, lead nitrate, and calcium chloride. The net ionic equations are: 1. \(Ba^{2+} + SO_4^{2-} \rightarrow BaSO_4\) 2. \(Pb^{2+} + SO_4^{2-} \rightarrow PbSO_4\) 3. \(Ca^{2+} + SO_4^{2-} \rightarrow CaSO_4\) For calcium ions, precipitates can form with sulfate ion, phosphate ion, and oxalate ion. The net ionic equations are: 1. \(Ca^{2+} + SO_4^{2-} \rightarrow CaSO_4\) 2. \(3Ca^{2+} + 2PO_4^{3-} \rightarrow Ca_3(PO_4)_2\) 3. \(Ca^{2+} + C_2O_4^{2-} \rightarrow CaC_2O_4\) For mercury(I) ions, precipitates can form with chloride ion, bromide ion, and iodide ion. The net ionic equations are: 1. \(Hg_2^{2+} + 2Cl^- \rightarrow Hg_2Cl_2\) 2. \(Hg_2^{2+} + 2Br^- \rightarrow Hg_2Br_2\) 3. \(Hg_2^{2+} + 2I^- \rightarrow Hg_2I_2\) For iron(III) ions, precipitates can form with hydroxide ion, phosphate ion, and sulfide ion. The net ionic equations are: 1. \(Fe^{3+} + 3OH^- \rightarrow Fe(OH)_3\) 2. \(Fe^{3+} + PO_4^{3-} \rightarrow FePO_4\) 3. \(2Fe^{3+} + 3S^{2-} \rightarrow Fe_2S_3\) For silver ions, precipitates can form with chloride ion, bromide ion, and iodide ion. The net ionic equations are: 1. \(Ag^+ + Cl^- \rightarrow AgCl\) 2. \(Ag^+ + Br^- \rightarrow AgBr\) 3. \(Ag^+ + I^- \rightarrow AgI\)

Step-by-step solution

Identify insoluble reagents with chloride ion

Using the general solubility rules, we can identify three reagents that would form insoluble products with chloride ion: silver nitrate (AgNO3), lead nitrate (Pb(NO3)2), and mercury(II) nitrate (Hg(NO3)2). These reagents would form silver chloride (AgCl), lead(II) chloride (PbCl2), and mercury(II) chloride (HgCl2) precipitates, respectively.

Write the net ionic equations

For each of the reactions with chloride ion, we can write the net ionic equations as follows: 1. Silver nitrate and chloride ion: \(Ag^+ + Cl^- \rightarrow AgCl\) 2. Lead nitrate and chloride ion: \(Pb^{2+} + 2Cl^- \rightarrow PbCl_2\) 3. Mercury(II) nitrate and chloride ion: \(Hg^{2+} + 2Cl^- \rightarrow HgCl_2\) **(b) Sulfate ion (SO4²-)**

Identify insoluble reagents with sulfate ion

Using the general solubility rules, we can identify three reagents that would form insoluble products with the sulfate ion: barium chloride (BaCl2), lead nitrate (Pb(NO3)₂), and calcium chloride (CaCl2). They would form barium sulfate (BaSO4), lead(II) sulfate (PbSO4), and calcium sulfate (CaSO4) precipitates, respectively.

Write the net ionic equations

For each of the reactions with sulfate ion, we can write the net ionic equations as follows: 1. Barium chloride and sulfate ion: \(Ba^{2+} + SO_4^{2-} \rightarrow BaSO_4\) 2. Lead nitrate and sulfate ion: \(Pb^{2+} + SO_4^{2-} \rightarrow PbSO_4\) 3. Calcium chloride and sulfate ion: \(Ca^{2+} + SO_4^{2-} \rightarrow CaSO_4\) **(c) Calcium ion (Ca²+)**

Identify insoluble reagents with calcium ion

Using the general solubility rules, we can identify three reagents that would form insoluble products with the calcium ion: sulfate ion (SO4²-), phosphate ion (PO4³-), and oxalate ion (C2O4²-). They would form calcium sulfate (CaSO4), calcium phosphate (Ca₃(PO₄)₂), and calcium oxalate (CaC2O4) precipitates, respectively.

Write the net ionic equations

For each of the reactions with the calcium ion, we can write the net ionic equations as follows: 1. Calcium ion and sulfate ion: \(Ca^{2+} + SO_4^{2-} \rightarrow CaSO_4\) 2. Calcium ion and phosphate ion: \(3Ca^{2+} + 2PO_4^{3-} \rightarrow Ca_3(PO_4)_2\) 3. Calcium ion and oxalate ion: \(Ca^{2+} + C_2O_4^{2-} \rightarrow CaC_2O_4\) **(d) Mercury(I) ion (Hg2²+)**

Identify insoluble reagents with mercury(I) ion

Using the general solubility rules, we can identify three reagents that would form insoluble products with the mercury(I) ion: chloride ion (Cl-), bromide ion (Br-), and iodide ion (I-). They would form mercury(I) chloride (Hg2Cl2), mercury(I) bromide (Hg2Br2), and mercury(I) iodide (Hg2I2) precipitates, respectively.

Write the net ionic equations

For each of the reactions with the mercury(I) ion, we can write the net ionic equations as follows: 1. Mercury(I) ion and chloride ion: \(Hg_2^{2+} + 2Cl^- \rightarrow Hg_2Cl_2\) 2. Mercury(I) ion and bromide ion: \(Hg_2^{2+} + 2Br^- \rightarrow Hg_2Br_2\) 3. Mercury(I) ion and iodide ion: \(Hg_2^{2+} + 2I^- \rightarrow Hg_2I_2\) **(e) Iron(III) ion (Fe³+)**

Identify insoluble reagents with iron(III) ion

Using the general solubility rules, we can identify three reagents that would form insoluble products with the iron(III) ion: hydroxide ion (OH-), phosphate ion (PO4³-), and sulfide ion (S²-). They would form iron(III) hydroxide (Fe(OH)3), iron(III) phosphate (FePO4), and iron(III) sulfide (Fe2S3) precipitates, respectively.

Write the net ionic equations

For each of the reactions with the iron(III) ion, we can write the net ionic equations as follows: 1. Iron(III) ion and hydroxide ion: \(Fe^{3+} + 3OH^- \rightarrow Fe(OH)_3\) 2. Iron(III) ion and phosphate ion: \(Fe^{3+} + PO_4^{3-} \rightarrow FePO_4\) 3. Iron(III) ion and sulfide ion: \(2Fe^{3+} + 3S^{2-} \rightarrow Fe_2S_3\) **(f) Silver ion (Ag+)**

Identify insoluble reagents with silver ion

Using the general solubility rules, we can identify three reagents that would form insoluble products with the silver ion: chloride ion (Cl-), bromide ion (Br-), and iodide ion (I-). They would form silver chloride (AgCl), silver bromide (AgBr), and silver iodide (AgI) precipitates, respectively.

Write the net ionic equations

For each of the reactions with the silver ion, we can write the net ionic equations as follows: 1. Silver ion and chloride ion: \(Ag^+ + Cl^- \rightarrow AgCl\) 2. Silver ion and bromide ion: \(Ag^+ + Br^- \rightarrow AgBr\) 3. Silver ion and iodide ion: \(Ag^+ + I^- \rightarrow AgI\)

Key concepts

Solubility Rules

Solubility rules are a set of guidelines used to predict whether an ionic compound will dissolve in water. These rules help determine if a product of a reaction is a soluble or insoluble compound. In aqueous chemistry, knowing these rules is crucial for predicting the outcome of mixing different ions in solutions.
Solubility rules can usually be summarized with the following points:

• Most nitrate (NO₃⁻) and acetate (CH₃COO⁻) salts are soluble.
• Most salts of alkali metals (like Na⁺ and K⁺) and ammonium (NH₄⁺) are soluble.
• Chloride (Cl⁻), bromide (Br⁻), and iodide (I⁻) salts are generally soluble except when paired with silver (Ag⁺), lead (Pb²⁺), or mercury (Hg²⁺).
• Most sulfate (SO₄²⁻) salts are soluble, except for those of barium (Ba²⁺), lead (Pb²⁺), and calcium (Ca²⁺).
• Most hydroxides (OH⁻) are insoluble, with exceptions such as those of the alkali metals.
• Phosphate (PO₄³⁻), carbonate (CO₃²⁻), and sulfide (S²⁻) salts are generally insoluble, again except with alkali metals and ammonium.

These rules are simplifications and there are exceptions, but they provide a useful starting point for predicting solubility in water.

Precipitation Reactions

Precipitation reactions occur when two soluble substances react in an aqueous solution to form an insoluble product, known as a precipitate. This insoluble product often appears as a cloudy suspension or solid in the solution.
These reactions can be predicted using the solubility rules. When two ionic solutions are mixed and an insoluble ionic compound is formed, a precipitation reaction has occurred. The key steps in understanding and identifying precipitation reactions include:

• Writing down the ions present in the solution before any reaction occurs.
• Using the solubility rules to determine if a combination of these ions can form an insoluble compound.
• Writing the net ionic equation to show the actual ions participating in forming the precipitate.

Net ionic equations for precipitation reactions only include the ions and molecules directly involved in the formation of the precipitate, omitting the spectator ions that do not change during the reaction. These equations highlight the essence of the precipitation process and help clarify understanding of the reaction dynamics.

Chemical Reagents

Chemical reagents are substances or compounds added to a system to cause a chemical reaction, or to see if a reaction occurs. In the context of precipitation reactions, reagents are chosen based on their ability to create a specific product or to separate particular ions in a solution.
Some common reagents used to test for precipitation include:

• Silver nitrate (AgNO₃), often used to test for chloride ions, as it forms a white precipitate of silver chloride (AgCl).
• Barium chloride (BaCl₂), used to test for sulfate ions, forming a white precipitate of barium sulfate (BaSO₄).
• Lead(II) nitrate (Pb(NO₃)₂), which can also be used to detect chloride and sulfate ions.

Choosing the correct reagent depends on the ions present in the solution and the compound you want to precipitate. Understanding how different reagents react with different ions based on the solubility rules helps in effectively using chemical reagents in reactions.

Aqueous Solution Chemistry

Aqueous solution chemistry focuses on the behavior of substances dissolved in water. Water's ability to dissolve a wide range of substances makes it a universal solvent, crucial for chemical reactions, especially in biological and environmental contexts.
Key aspects of aqueous solution chemistry include:

• The dissociation of electrolytes into ions in solution. Ionic compounds break apart into their constituent ions when dissolved in water.
• Conductivity. The presence of ions in solution enhances its electrical conductivity.
• Reaction mechanisms. Understanding how different ions interact in solution is fundamental for predicting reaction outcomes, such as those in precipitation reactions or acid-base neutralizations.

An important concept in this field is the equilibrium between dissolved ions and undissolved salts, guiding predictions on reaction direction and extent. Mastery of aqueous solution chemistry is essential for predicting and explaining reactions involving soluble and insoluble compounds.