Applying Solubility Rules to the Problem

Oct 13, 2025 by pinkandtrash.com 49 views

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Understanding the Problem

When two solutions are mixed, bringing together ions of $Na^{+}, PO_4^{3-}, V^{3+},$ and $Cl^{-}$ , a new compound is formed. However, not all compounds are stable in solution, and some may precipitate out as a solid. In this article, we will use solubility rules to identify the composition of the salt that precipitates out of the solution.

Solubility Rules: A Guide to Precipitation

Before we dive into the problem, it's essential to understand the solubility rules. These rules help us predict which compounds are soluble and which are not. Here are some of the most common solubility rules:

Group 1A cations (alkali metals) and Group 2A cations (alkaline earth metals) are generally soluble in water. This means that compounds containing these cations, such as $NaCl$ and $CaCO_3$ , are usually soluble.
Nitrates (NO_3^-) and acetates (CH_3COO^-) are generally soluble in water. This means that compounds containing these anions, such as $NaNO_3$ and $Ca(CH_3COO)_2$ , are usually soluble.
Chlorides (Cl^-), bromides (Br^-), and iodides (I^-) are generally soluble in water, except for those of silver (Ag^+), lead (Pb^2+), and mercury (Hg_2^2+). This means that compounds containing these anions, such as $NaCl$ and $CaBr_2$ , are usually soluble, except for those containing silver, lead, or mercury.
Sulfates (SO_4^{2-}) are generally soluble in water, except for those of barium (Ba^2+), strontium (Sr^2+), and lead (Pb^2+). This means that compounds containing this anion, such as $Na_2SO_4$ and $CaSO_4$ , are usually soluble, except for those containing barium, strontium, or lead.
Carbonates (CO_3^{2-}), phosphates (PO_4^{3-}), and silicates (SiO_3^{2-}) are generally insoluble in water, except for those of sodium (Na^+), potassium (K^+), and ammonium (NH_4^+). This means that compounds containing these anions, such as $Na_2CO_3$ and $K_2PO_4$ , are usually insoluble, except for those containing sodium, potassium, or ammonium.

Applying Solubility Rules to the Problem

Now that we have a good understanding of the solubility rules, let's apply them to the problem. We are given the ions $Na^{+}, PO_4^{3-}, V^{3+},$ and $Cl^{-}$ . We need to determine which compound will precipitate out of the solution.

First, let's consider the possible compounds that can be formed using these ions. We can use the solubility rules to determine which compounds are soluble and which are not.

$NaPO_4$ : This compound contains the phosphate anion, which is generally insoluble in water, except for those of sodium (Na^+). However, since we have a vanadium (V^3+) ion present, this compound is likely to be insoluble.
$NaCl$ : This compound contains the chloride anion, which is generally soluble in water, except for those of silver (Ag^+), lead (Pb^2+), and mercury (Hg_2^2+). Since we don't have any of these ions present, this compound is likely to be soluble.
$VPO_4$ : This compound contains the phosphate anion and the vanadium (V^3+) ion. Since the phosphate anion is generally insoluble in water, except for those of sodium (Na^+), and we don't have any sodium ions present, this compound is likely to be insoluble.
$VCl_3$ : This compound contains the chloride anion and the vanadium (V^3+) ion. Since the chloride anion is generally soluble in water, except for those of silver (Ag^+), lead (Pb^2+), and mercury (Hg_2^2+), and we don't have any of these ions present, this compound is likely to be soluble.

Conclusion

Based on the solubility rules, we can conclude that the compound that will precipitate out of the solution is $VPO_4$ . This compound contains the phosphate anion and the vanadium (V^3+) ion, which are both insoluble in water, except for those of sodium (Na^+). Since we don't have any sodium ions present, this compound is likely to be insoluble.

References

Petrucci, R. H., Harwood, W. S., Herring, F. G., & Madura, J. D. (2007). General chemistry: Principles and modern applications. Pearson Prentice Hall.
Atkins, P. W., & De Paula, J. (2010). Physical chemistry. Oxford University Press.

Glossary

Solubility rules: These are guidelines that help us predict which compounds are soluble and which are not.
Insoluble: A compound that is not soluble in water.
Soluble: A compound that is soluble in water.
Cations: Positively charged ions.
Anions: Negatively charged ions.

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Understanding the Problem

Q&A: Precipitation of Ions

Q: What are the solubility rules?

A: The solubility rules are guidelines that help us predict which compounds are soluble and which are not. They are based on the properties of the ions involved and the type of compound formed.

Q: What are the most common solubility rules?

A: The most common solubility rules are:

Group 1A cations (alkali metals) and Group 2A cations (alkaline earth metals) are generally soluble in water.
Nitrates (NO_3^-) and acetates (CH_3COO^-) are generally soluble in water.
Chlorides (Cl^-), bromides (Br^-), and iodides (I^-) are generally soluble in water, except for those of silver (Ag^+), lead (Pb^2+), and mercury (Hg_2^2+).
Sulfates (SO_4^{2-}) are generally soluble in water, except for those of barium (Ba^2+), strontium (Sr^2+), and lead (Pb^2+).
Carbonates (CO_3^{2-}), phosphates (PO_4^{3-}), and silicates (SiO_3^{2-}) are generally insoluble in water, except for those of sodium (Na^+), potassium (K^+), and ammonium (NH_4^+).

Q: How do I apply the solubility rules to a problem?

A: To apply the solubility rules to a problem, you need to identify the ions involved and the type of compound formed. Then, you can use the solubility rules to determine which compounds are soluble and which are not.

Q: What is the difference between soluble and insoluble compounds?

A: Soluble compounds are those that can dissolve in water, while insoluble compounds are those that cannot dissolve in water.

Q: What are some examples of soluble and insoluble compounds?

A: Some examples of soluble compounds are:

$NaCl$ (sodium chloride)
$Ca(NO_3)_2$ (calcium nitrate)
$K_2SO_4$ (potassium sulfate)

Some examples of insoluble compounds are:

$CaCO_3$ (calcium carbonate)
$VPO_4$ (vanadium phosphate)
$AgCl$ (silver chloride)

Q: How do I determine which compound will precipitate out of a solution?

A: To determine which compound will precipitate out of a solution, you need to identify the ions involved and the type of compound formed. Then, you can use the solubility rules to determine which compounds are soluble and which are not.

Conclusion

In this article, we have discussed the solubility rules and how to apply them to a problem. We have also answered some common questions about precipitation of ions. By understanding the solubility rules and how to apply them, you can predict which compounds will precipitate out of a solution.

References

Petrucci, R. H., Harwood, W. S., Herring, F. G., & Madura, J. D. (2007). General chemistry: Principles and modern applications. Pearson Prentice Hall.
Atkins, P. W., & De Paula, J. (2010). Physical chemistry. Oxford University Press.

Glossary

Solubility rules: These are guidelines that help us predict which compounds are soluble and which are not.
Insoluble: A compound that is not soluble in water.
Soluble: A compound that is soluble in water.
Cations: Positively charged ions.
Anions: Negatively charged ions.