Question

Which anions form compounds that are generally soluble in water: \(\mathrm{CO}_{3}^{2-}, \mathrm{NO}_{3}^{-}, \mathrm{Br}^{-}, \mathrm{SO}_{4}^{2-}, \mathrm{OH}^{-}, \mathrm{PO}_{4}^{3-} ?\)

Short answer

The anions that form compounds that are generally soluble in water are nitrate (NO₃⁻), bromide (Br⁻), and sulfate (SO₄²⁻), according to the general solubility rules. However, there may be exceptions, and the solubility of specific compounds should be checked if needed.

Step-by-step solution

Review the solubility rules

First, let's recall the solubility rules that help us predict the solubility of ionic compounds in water: 1. Salts containing Group 1 elements (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺) and ammonium ion (NH₄⁺) are soluble. 2. Salts containing nitrate (NO₃⁻), acetate (C₂H₃O₂⁻), and perchlorate (ClO₄⁻) are soluble. 3. Halides (Cl⁻, Br⁻, I⁻) are soluble, with the exception of those formed with Ag⁺, Hg₂²⁺, and Pb²⁺. 4. Sulfates (SO₄²⁻) are soluble, with the exception of those formed with Ba²⁺, Sr²⁺, Pb²⁺, Ca²⁺, and Hg₂²⁺. 5. Carbonates (CO₃²⁻), phosphates (PO₄³⁻), chromates (CrO₄²⁻), and sulfides (S²⁻) are insoluble, except those formed with Group 1 elements and NH₄⁺. 6. Hydroxides (OH⁻) are insoluble, except those formed with Group 1 elements, NH₄⁺, Ca²⁺, Sr²⁺, and Ba²⁺. *Keep in mind that these rules provide a general guideline, and there could be some exceptions.

Determine solubility of the given anions

Using the solubility rules, we can determine the solubility of compounds formed with each given anion: - Carbonate (CO₃²⁻): Rule 5 tells us that carbonates are generally insoluble, with some exceptions. - Nitrate (NO₃⁻): According to rule 2, nitrates are soluble. - Bromide (Br⁻): Rule 3 indicates that halides are soluble, with few exceptions. - Sulfate (SO₄²⁻): Rule 4 states that sulfates are soluble, with some exceptions. - Hydroxide (OH⁻): According to rule 6, hydroxides are generally insoluble, with few exceptions. - Phosphate (PO₄³⁻): Rule 5 states that phosphates are generally insoluble, with some exceptions.

List the anions that form generally soluble compounds

Based on our analysis, the anions that form compounds that are generally soluble in water are: - Nitrate (NO₃⁻) - Bromide (Br⁻) - Sulfate (SO₄²⁻) These are the anions that will often form soluble compounds in water, according to the general solubility rules. Please be aware that there may be exceptions to these rules, and the solubility of specific compounds should be checked if needed.

Key concepts

Ionic Compounds Solubility

Understanding the solubility of ionic compounds in water is essential for students studying chemistry, as it applies to various areas including chemical reactions and analysis. Solubility rules are guidelines that predict whether an ionic compound will dissolve (be soluble) in water.

When we look at an ionic compound, we are observing a substance made from a positively charged ion, known as a cation, and a negatively charged ion, known as an anion. The solubility of an ionic compound in water is influenced by the nature of these ions; that is, certain anions and cations can cause a compound to be soluble or insoluble in water.

For instance, most compounds containing Group 1 elements, which include lithium (Li⁺), sodium (Na⁺), potassium (K⁺), rubidium (Rb⁺), cesium (Cs⁺), as well as the ammonium ion (NH₄⁺), are generally soluble. This is because these ions form strong ionic bonds with water molecules, leading to the dissolution of the compound.

To simplify, let's think of solubility as a match-up between ions. Some pairs get along well and mix into water, making the compound soluble. However, others don’t pair up as nicely, which leads to the compound being insoluble—remaining undissolved in water.

Improving Solubility Predictions

• Review the periodic table to become familiar with the groups of elements that affect solubility.
• Memorize key solubility rules to quickly predict outcomes in different scenarios.
• Conduct experiments to observe solubility firsthand for various compounds, as practical experience reinforces theoretical knowledge.
• Use online solubility calculators and databases to check the solubility of specific compounds when in doubt.

Soluble Anions

In our study of solubility, anions play a crucial role. Certain anions are almost always a sign that the compound they form will be soluble in water. These include the nitrate ion (NO₃⁻), acetate ion (C₂H₃O₂⁻), and perchlorate ion (ClO₄⁻). The rule of thumb is that if you spot one of these anions, the compound is likely to dissolve in water.

However, there are also anions that are typically found in compounds that are insoluble or partially soluble, such as carbonates (CO₃²⁻), phosphates (PO₄³⁻), and hydroxides (OH⁻). But, as with nearly every rule, there are exceptions. For example, while most carbonates are insoluble, those paired with Group 1 cations or ammonium will dissolve.

Factors Influencing Anion Solubility

• Chemical composition: The nature of the anion itself will inherently influence solubility.
• pH of the solution: Some anions like phosphates and carbonates are more soluble in acidic conditions.
• Presence of complexing agents: Certain chemicals can interact with anions to increase their solubility.

To best apply these rules, pay close attention to both the anion in question and the cation it is paired with, as the combination is key to determining solubility.

Water Solubility Chemistry

Water, often referred to as the 'universal solvent', has a unique ability to dissolve many substances, and this includes a wide variety of ionic compounds. The chemistry of water solubility is grounded in the polarity of water molecules. Each water molecule has a slightly positive charge on one side and a slightly negative charge on the other, which allows it to interact with and dissolve many other polar substances, including salts.

When an ionic compound comes into contact with water, the water molecules surround the ions. The positively charged hydrogen atoms in the water are attracted to the negatively charged anions, while the negatively charged oxygen atoms are attracted to the positively charged cations. This interaction can cause the ionic compound to dissociate into its individual ions, becoming 'soluble'.

Key Factors Affecting Water Solubility

• Temperature: Generally, increasing temperature enhances the solubility of most compounds in water.
• Pressure: It has less effect on solids and liquids, but pressure can significantly affect the solubility of gases in water.
• Nature of solute and solvent: The molecular structure, polarity, and ionization will determine the compatibility between solute and solvent.

Understanding these principles will help students predict the behavior of substances in water and is vital for tasks such as mixture separation, chemical synthesis, and biological applications.