Ch.4 - Reactions in Aqueous Solution

Problem 21

Chapter 4, Problem 21

Using solubility guidelines, predict whether each of the following compounds is soluble or insoluble in water: (a) MgBr₂ (b) NH₄OH (c) Ni(CH₃COO)₂ (d) AgNO₃ (e) FeCO₃.

Verified step by step guidance

Step 1: Understand the solubility rules. Some of the key rules are: (1) All nitrates (NO3-) are soluble. (2) All salts of alkali metals (Group 1 elements) and ammonium (NH4+) are soluble. (3) All chlorides (Cl-), bromides (Br-), and iodides (I-) are soluble, except those of silver (Ag+), lead (Pb2+), and mercury (Hg2+). (4) All sulfates (SO4^2-) are soluble, except those of barium (Ba2+), strontium (Sr2+), lead (Pb2+), calcium (Ca2+), silver (Ag+), and mercury (Hg2+).

Step 2: Identify the ions in the compound. In this case, MgBr2 is made up of Mg2+ and Br- ions.

Step 3: Apply the solubility rules to the ions in the compound. According to the rules, all bromides (Br-) are soluble except those of silver (Ag+), lead (Pb2+), and mercury (Hg2+). Since Mg2+ is not one of the exceptions, MgBr2 is soluble in water.

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Key Concepts

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

Solubility Rules

Solubility rules are a set of guidelines used to predict whether ionic compounds will dissolve in water. These rules take into account the nature of the ions involved, such as their charge and size, and categorize them into soluble and insoluble groups. For example, most salts containing alkali metal ions or ammonium ions are soluble, while many metal hydroxides and carbonates are generally insoluble.

Ionic Compounds

Ionic compounds are formed from the electrostatic attraction between positively charged cations and negatively charged anions. Their solubility in water depends on the strength of these ionic bonds compared to the interactions with water molecules. Compounds like MgBr<sub>2</sub> consist of magnesium cations and bromide anions, and their solubility can be assessed using established solubility rules.

Hydration Energy

Hydration energy refers to the energy released when ions are surrounded by water molecules. This process is crucial for the dissolution of ionic compounds in water. If the hydration energy is greater than the lattice energy (the energy holding the ions together in the solid), the compound will dissolve. For MgBr<sub>2</sub>, the hydration energy of the magnesium and bromide ions plays a significant role in determining its solubility.

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Acetone, CH3COCH3, is a nonelectrolyte; hypochlorous acid, HClO, is a weak electrolyte; and ammonium chloride, NH4Cl, is a strong electrolyte. (a) What are the solutes present in aqueous solutions of each compound? What solute particles are present in an aqueous solution of HClO?

Textbook Question

Acetone, CH₃COCH₃, is a nonelectrolyte; hypochlorous acid, HClO, is a weak electrolyte; and ammonium chloride, NH₄Cl, is a strong electrolyte. (b) If 0.1 mol of each compound is dissolved in solution, which one contains 0.2 mol of solute particles, which contains 0.1 mol of solute particles, and which contains somewhere between 0.1 and 0.2 mol of solute particles?

Textbook Question

Predict whether each of the following compounds is soluble in water: (a) MgS (b) Cr(OH)₃ (c) ZnCl₂ (d) Pb₃(PO₄)₂ (e) Sr(CH₃COO)₂.

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Textbook Question

Will precipitation occur when the following solutions are mixed? If so, write a balanced chemical equation for the reaction. (a) Ca(CH₃COO)₂ and NaOH (b) K₂CO₃ and NH₄NO₃, (c) Na₂S and FeCl₃.

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Textbook Question

Identify the precipitate (if any) that forms when the following solutions are mixed, and write a balanced equation for each reaction. (a) NH₄I and CuCl₂ (b) LiOH and MnCl₂ (c) K₃PO₄ and CoSO₄

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Using solubility guidelines, predict whether each of the following compounds is soluble or insoluble in water: (a) MgBr2 (b) NH4OH (c) Ni(CH3COO)2 (d) AgNO3 (e) FeCO3.

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Key Concepts

Solubility Rules

Ionic Compounds

Hydration Energy

Using solubility guidelines, predict whether each of the following compounds is soluble or insoluble in water: (a) MgBr₂ (b) NH₄OH (c) Ni(CH₃COO)₂ (d) AgNO₃ (e) FeCO₃.