Question

Which of the following ions form compounds with \(\mathrm{Ag}^{+}\) that are generally soluble in water? a. \(S^{2-}\) b. \(\mathrm{Cl}^{-}\) c. \(\mathrm{NO}_{3}^{-}\) d. \(\mathrm{SO}_{4}^{2-}\) e. \(\mathrm{Na}^{+}\)

Short answer

The ion that forms a soluble compound with \(\mathrm{Ag}^{+}\) is \(\mathrm{NO}_{3}^{-}\). Therefore, the correct answer is c. \(\mathrm{NO}_{3}^{-}\).

Step-by-step solution

Understanding Solubility Rules

To answer this question, we will need to understand the solubility rules for ionic compounds in water. Here are some general solubility rules to keep in mind: 1. Compounds containing alkali metal ions (\(\mathrm{Li}^{+}\), \(\mathrm{Na}^{+}\), \(\mathrm{K}^{+}\), \(\mathrm{Rb}^{+}\) and \(\mathrm{Cs}^{+}\)) and the ammonium ion (\(\mathrm{NH}_{4}^{+}\)) are soluble. 2. Nitrates (\(\mathrm{NO}_{3}^{-}\)), acetates (\(\mathrm{CH}_{3}\mathrm{COO}^{-}\)) and perchlorates (\(\mathrm{ClO}_{4}^{-}\)) are soluble. 3. Chloride (\(\mathrm{Cl}^{-}\)), bromide (\(\mathrm{Br}^{-}\)), and iodide (\(\mathrm{I}^{-}\)) compounds are soluble, except those of silver (\(\mathrm{Ag}^{+}\)), lead (\(\mathrm{Pb}^{2+}\)) and mercury (\(\mathrm{Hg}_{2}^{2+}\)). 4. Sulfate (\(\mathrm{SO}_{4}^{2-}\)) compounds are soluble, except those of barium (\(\mathrm{Ba}^{2+}\)), calcium (\(\mathrm{Ca}^{2+}\)), strontium (\(\mathrm{Sr}^{2+}\)), lead (\(\mathrm{Pb}^{2+}\)), and silver (\(\mathrm{Ag}^{+}\)). 5. Sulfides (\(S^{2-}\)), carbonates (\(\mathrm{CO}_{3}^{2-}\)), phosphates (\(\mathrm{PO}_{4}^{3-}\)) and chromates (\(\mathrm{CrO}_{4}^{2-}\)) are generally insoluble. Now we will go through each ion in the question and see if the compound formed with \(\mathrm{Ag}^{+}\) will be soluble in water.

Evaluate the Ions

a. \(S^{2-}\): Compounds containing sulfide are generally insoluble, so \(\mathrm{Ag}_2S\) should be insoluble. b. \(\mathrm{Cl}^{-}\): According to rule 3, most chloride compounds are soluble, except those of silver, so \(\mathrm{AgCl}\) will be insoluble. c. \(\mathrm{NO}_{3}^{-}\): Nitrates are soluble as per rule 2; therefore, \(\mathrm{AgNO}_{3}\) should be soluble in water. d. \(\mathrm{SO}_{4}^{2-}\): Rule 4 states that most sulfate compounds are soluble, except those of silver, so \(\mathrm{Ag}_{2}\mathrm{SO}_{4}\) will be insoluble. e. \(\mathrm{Na}^{+}\): Since we are looking for the anions that can form soluble compounds with \(\mathrm{Ag}^{+}\), this option is not relevant (as \(\mathrm{Na}^{+}\) is a cation).

Conclusion

Based on our evaluation of each ion option, we can conclude that the ion that forms a soluble compound with \(\mathrm{Ag}^{+}\) is \(\mathrm{NO}_{3}^{-}\). So, the correct answer is: c. \(\mathrm{NO}_{3}^{-}\)

Key concepts

Ionic Compounds

When atoms come together, they can form compounds through the transfer of electrons, leading to the creation of ions. Ionic compounds are formed by the attraction between positively charged ions (cations) and negatively charged ions (anions). This ionic bond is quite strong and forms a crystal lattice structure in solid form.
Examples of common ionic compounds include table salt ( NaCl ) and silver nitrate ( AgNO_3 ).

• Cations are typically metal ions and have a positive charge because they give away electrons.
• Anions, on the other hand, are usually non-metal ions which have a negative charge because they gain electrons.

Understanding how these ions come together helps in predicting the properties of the compounds they form, such as solubility.

Chemical Ions

Ions are atoms or molecules that have gained or lost one or more electrons, resulting in a net electric charge. The process of forming an ion is known as ionization, which can occur through various chemical reactions. Chemical ions are essential players in the formation of various compounds, including those that dissolve in water to form solutions.
Ions can either be cations or anions:

• Cations are positively charged ions, like Na^+ and Ag^+ , as they have more protons than electrons.
• Anions are negatively charged ions, such as Cl^- and NO_3^- , due to having more electrons than protons.

In a solution, these ions play critical roles in conduction of electricity and chemical reactions. Recognizing which ions are formed in a compound aids in predicting its behavior in different solvents.

Solubility Exceptions

The solubility of ionic compounds in water isn't always straightforward, and there are exceptions to be aware of. While many ionic compounds are soluble, meaning they dissolve in water, some do not. Solubility rules help us predict whether a compound will dissolve:

• Most compounds of alkali metal ions ( Li^+ , Na^+ ) and NH_4^+ are soluble.
• Nitrates ( NO_3^- ), acetates, and perchlorates are soluble, with few exceptions.
• Compounds with Cl^- , Br^- , and I^- are usually soluble, except when paired with Ag^+ , Pb^{2+} , or Hg_2^{2+} .

It is vital to remember these exceptions because they explain why some combinations of ions resist dissolving. For example, while Cl^- typically forms soluble compounds, in the presence of Ag^+ , the compound AgCl is insoluble. By being aware of such exceptions, we can better predict the outcome of mixing ions.