Question

Predict whether each of the following compounds is soluble in water: (a) AgI, (b) \(\mathrm{Na}_{2} \mathrm{CO}_{3}\), (c) \(\mathrm{BaCl}_{2}\), (d) \(\mathrm{Al}(\mathrm{OH})_{3}\), (e) \(\mathrm{Zn}\left(\mathrm{CH}_{3} \mathrm{COO}\right)_{2}\).

Short answer

Using the solubility rules, we can predict the solubility of each compound in water: (a) AgI: Insoluble (b) Na₂CO₃: Soluble (c) BaCl₂: Soluble (d) Al(OH)₃: Insoluble (e) Zn(CH₃COO)₂: Soluble

Step-by-step solution

Identify the ions in each compound

For each compound, identify the cation (positively charged ion) and the anion (negatively charged ion). Apply the solubility rules to determine whether the compound is soluble in water or not. (a) AgI: Ag⁺ (silver) and I⁻ (iodide) (b) Na₂CO₃: Na⁺ (sodium) and CO₃²⁻ (carbonate) (c) BaCl₂: Ba²⁺ (barium) and Cl⁻ (chloride) (d) Al(OH)₃: Al³⁺ (aluminium) and OH⁻ (hydroxide) (e) Zn(CH₃COO)₂: Zn²⁺ (zinc) and CH₃COO⁻ (acetate)

Apply the solubility rules

The following solubility rules can be used for this exercise: 1. Most group 1 (alkali metals) and ammonium compounds are soluble. 2. Most nitrates, acetates (CH₃COO⁻), and perchlorates are soluble. 3. Most halogens (Cl⁻, Br⁻, I⁻) are soluble, except when combined with Ag⁺, Pb2⁺, and Hg₂²⁺. 4. Most sulfates are soluble, except when combined with Ba²⁺, Pb²⁺, Ca²⁺, and Sr²⁺. 5. Most hydroxides are insoluble, except when combined with group 1, Ca²⁺, Sr²⁺, and Ba²⁺. 6. Most carbonates (CO₃²⁻), phosphates (PO₄³⁻), chromates (CrO₄²⁻), and sulfides are insoluble unless combined with group 1 or ammonium.

Determine the solubility of each compound based on the solubility rules

(a) AgI: The compound contains I⁻ (a halogen) and Ag⁺. According to rule 3, this compound is insoluble in water. (b) Na₂CO₃: The compound contains Na⁺ (a group 1 element) and CO₃²⁻. According to rule 1, this compound is soluble in water. (c) BaCl₂: The compound contains Ba²⁺ and Cl⁻ (a halogen). According to rule 3, this compound is soluble in water, because Ba²⁺ is not an exception for halogens. (d) Al(OH)₃: The compound contains Al³⁺ and OH⁻. According to rule 5, this compound is insoluble in water, because Al³⁺ is not an exception for hydroxides. (e) Zn(CH₃COO)₂: The compound contains Zn²⁺ and CH₃COO⁻ (acetate). According to rule 2, this compound is soluble in water.

Summarize the solubility results

Based on the solubility rules applied to each compound: (a) AgI: Insoluble (b) Na₂CO₃: Soluble (c) BaCl₂: Soluble (d) Al(OH)₃: Insoluble (e) Zn(CH₃COO)₂: Soluble

Key concepts

Solubility in Water

Understanding how solubility in water works is essential for predicting the behavior of substances in various chemical processes. Solubility refers to the maximum amount of a substance that can dissolve in a solvent at a given temperature and pressure. Water, often called the 'universal solvent', can dissolve many compounds due to its polar nature.

Solubility is governed by the interplay between the forces of attraction among the solute particles and between the solute particles and solvent. If the attractions between the solvent molecules (water) and the solute are strong enough, then the substance will dissolve. Temperature also plays a crucial role; generally, as temperature increases, so does solubility for most soluble substances.

For the exercise at hand, the solubility rules are key to determining whether a compound will dissolve in water. Knowing these rules allows us to predict that sodium carbonate, Na₂CO₃, will dissolve due to its positive cation being from group 1, which are generally soluble in water.

Ionic Compounds

Ionic compounds are chemical compounds made up of ions that are held together by ionic bonds. The ions are atoms or molecules that have gained or lost electrons and thus have a net negative or positive charge. In the context of solubility, when ionic compounds dissolve in water, the cations and anions separate and disperse uniformly throughout the solution.

Ionic compounds typically dissolve well in polar solvents such as water, but there are exceptions based on the charge and size of the ion, and the specific ionic lattice structure. For instance, silver iodide (AgI) does not dissolve in water despite being ionic because the solubility rules indicate the exception due to the presence of the Ag⁺ ion. These nuances make the study of ionic compounds intriguing, as one must consider both the properties of the ions involved and the overarching solubility rules.

Soluble and Insoluble Compounds

In chemistry, distinguishing between soluble and insoluble compounds is a fundamental skill. Soluble compounds are those that dissolve in a solvent, such as water, to a significant extent. Conversely, insoluble compounds do not dissolve appreciably in a solvent.

The solubility rules help predict the solubility of ionic compounds in water. For example, hydroxides are generally insoluble, but an important exception is when they are combined with certain cations like those from the Group 1 elements. This rule explains why Al(OH)₃ is insoluble, as it does not fall within the exceptions listed. Understanding and applying these rules allow scientists to predict the behavior of substances in various environments, which is crucial in fields ranging from pharmacology to environmental science.