Solubility Rules

The Organic Chemistry Tutor
1 Jul 202006:19
EducationalLearning
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TLDRThe video script offers an insightful guide on determining the solubility of compounds in water using solubility rules. It explains that compounds are considered soluble if they dissolve in water, while insoluble compounds do not. The general rule is that group one metal ions, such as sodium, potassium, lithium, and ammonium, as well as nitrate and acetate polyatomic ions, are always soluble. Halides are typically soluble except for silver, lead, and mercury compounds. Sulfates are generally soluble except with certain group two metals and lead. Hydroxides are usually insoluble, but exceptions include group one metals, ammonium, and heavy group 2 alkaline earth metals. Sulfide, carbonate, and phosphate ions are generally insoluble but become soluble when paired with group 1 metal cations. The video provides examples to illustrate these rules, such as sodium phosphate being soluble and lead sulfate being insoluble. It concludes by encouraging viewers to apply these rules to determine the solubility of various compounds, thereby enhancing their understanding of chemical solubility.

Takeaways
  • 🔍 Soluble compounds dissolve in water, while insoluble ones do not.
  • 🌟 Group 1 metal ions (like sodium, potassium, lithium, and rubidium) and ammonium are always soluble.
  • 🌀 Polyatomic ions such as nitrate and acetate are universally soluble with few exceptions.
  • 🧪 Halides (chloride, bromide, iodide) are generally soluble, except when combined with silver, lead(II), and mercury(II).
  • 📊 Sulfates are soluble except when paired with barium, strontium, lead(II), and sometimes calcium.
  • ⚗️ Hydroxides are typically insoluble, except with group 1 metals, ammonium, and heavy group 2 metals like calcium, strontium, and barium.
  • 🔬 Compounds with sulfide, carbonate, phosphate, and chromate ions are generally insoluble, but dissolve with group 1 metals and ammonium.
  • 🔧 Use solubility rules effectively to determine if a compound like sodium phosphate or potassium chloride is soluble or insoluble.
  • 🚫 Lead(II) nitrate is soluble due to the nitrate ion, despite lead’s general insolubility with sulfates.
  • 💧 Practical exercises using solubility rules help reinforce the concepts and ensure understanding.
Q & A

  • What determines if a compound is soluble or insoluble in water?

    -A compound's solubility in water is determined by its chemical composition and the solubility rules. Soluble compounds dissolve in water, while insoluble compounds do not.

  • Which group of metal ions are always soluble in water?

    -Group one metal ions, such as sodium (Na), potassium (K), lithium (Li), and rubidium (Rb), are always soluble in water.

  • Is ammonium always soluble in water?

    -Yes, ammonium is always soluble in water, following the general solubility rules.

  • What are the two polyatomic ions that are generally soluble in water?

    -The two polyatomic ions that are generally soluble in water are nitrate (NO3-) and acetate (CH3COO-).

  • What are the exceptions to the general solubility of halides?

    -The exceptions to the general solubility of halides are silver (Ag), lead (Pb2+), and mercury (Hg2+).

  • Why is magnesium hydroxide considered to be somewhat soluble in water?

    -Magnesium hydroxide is considered somewhat soluble in water because it has a very low solubility, but it is still higher than that of other hydroxide compounds below magnesium in the same group.

  • What is the general solubility rule for sulfates?

    -Sulfates are generally soluble in water, with the exception of certain group two metals like calcium (Ca), barium (Ba), strontium (Sr), and lead (Pb2+).

  • How do you represent a compound that dissolves in water?

    -A compound that dissolves in water is represented using the phase 'aq', which stands for aqueous.

  • What is the general rule for the solubility of carbonates?

    -Carbonates are generally insoluble, but they become soluble when paired with group 1 metal cations like sodium (Na), potassium (K), and lithium (Li), and with ammonium (NH4+).

  • Why is silver chloride considered insoluble in water?

    -Silver chloride (AgCl) is considered insoluble in water because silver (Ag) is an exception to the general solubility of chlorides.

  • What is the solubility of barium hydroxide in water?

    -Barium hydroxide (Ba(OH)2) is soluble in water, which is an exception to the general rule that hydroxides are insoluble.

  • How can one use the solubility rules to determine if a compound is soluble or insoluble?

    -One can use the solubility rules by identifying the metal ions, polyatomic ions, and other components of the compound and applying the general rules to predict whether the compound will dissolve in water or remain insoluble.

Outlines
00:00
🧪 Solubility Rules for Ionic Compounds

This paragraph introduces the concept of solubility and insolubility in water for ionic compounds. It outlines general solubility rules, stating that compounds with group one metal ions (sodium, potassium, lithium, rubidium) and ammonium are always soluble. Additionally, nitrate and acetate polyatomic ions are also soluble, with a few exceptions like silver, lead 2+, and mercury 2+. Halides are generally soluble except for fluorides, which have different exceptions. Sulfates are usually soluble except for certain group two metals and lead 2+. Hydroxides are typically insoluble except when paired with group one metals, ammonium, and heavy group 2 alkaline earth metals. Lastly, sulfide, carbonate, and phosphate ions are generally insoluble but become soluble when paired with group 1 metal cations or ammonium. The paragraph concludes with an invitation to apply these rules to example problems to determine the solubility of various compounds.

05:00
📚 Application of Solubility Rules in Practice

The second paragraph delves into applying the previously discussed solubility rules to specific examples. It demonstrates how to determine the solubility of sodium phosphate, potassium chloride, silver chloride, lead 2 nitrate, potassium sulfate, and potassium hydroxide. For each compound, the paragraph explains the rule that applies and the resulting solubility, using 'aq' to denote aqueous (soluble) and 's' for solid (insoluble). The paragraph also addresses barium hydroxide, magnesium hydroxide, lithium carbonate, magnesium phosphate, ammonium, silver nitrate, and lead iodide, providing their solubility status based on the established rules. It concludes with a suggestion to pause and attempt the examples independently before continuing with the video.

Mindmap
Keywords
💡Solubility
Solubility refers to the ability of a substance to dissolve in a solvent, such as water. In the context of the video, solubility is the main theme as it discusses the solubility rules to determine whether a compound is soluble or insoluble in water. For example, the video states that a 'soluble compound is one that dissolves in water,' which is essential for understanding the solubility rules.
💡Ionic Compound
An ionic compound is formed by the electrostatic attraction between oppositely charged ions, typically a metal and a non-metal. The video uses ionic compounds as the primary subject for applying solubility rules, emphasizing that the solubility of these compounds is determined by the types of ions they contain.
💡Group 1 Metal Ions
Group 1 metal ions include sodium, potassium, lithium, and rubidium. The video highlights that these ions are always soluble in water, which is a general rule in solubility. For instance, when discussing sodium phosphate, the video states it is soluble because 'anytime you see a group one metal ion like sodium... it's going to be soluble.'
💡Ammonium
Ammonium is a polyatomic ion that, according to the video, is always soluble in water. It is an important exception to the general rules, as it consistently forms soluble compounds regardless of the anion it is paired with, as mentioned in the script: 'Ammonium is also always soluble.'
💡Polyatomic Ions
Polyatomic ions are groups of atoms that act as a single ion with a charge. The video mentions nitrate and acetate as examples of polyatomic ions that are always soluble. This is significant as it is part of the general rules for predicting solubility, as stated: 'if you see any of these two polyatomic ions, nitrate acetate, it's always soluble.'
💡Halides
Halides are compounds containing halogens, such as chloride, bromide, and iodide. The video explains that halides are generally soluble, with specific exceptions like silver, lead 2+, and mercury 2+. For example, 'the halides like chloride bromide, iodide these are generally soluble,' but with noted exceptions that affect solubility.
💡
💡Sulfates
Sulfates are compounds containing the sulfate ion (SO4^2-). The video states that sulfates are generally soluble, with exceptions for certain group two metals like calcium, barium, and strontium, as well as lead 2+. This is a key point in the solubility rules, as demonstrated when discussing lead 2-sulfate: 'sulfates are generally soluble, but lead is an exception.'
💡Hydroxides
Hydroxides are compounds containing the hydroxide ion (OH^-). The video explains that hydroxides are generally insoluble, except when paired with group one metals or certain group 2 alkaline earth metals. Magnesium hydroxide is mentioned as an exception, being 'somewhat soluble,' which is a key distinction in the solubility rules.
💡Sulfide, Carbonate, Phosphate
These are anionic groups that, along with chromate, are generally found in insoluble compounds. However, the video specifies that they are soluble when paired with group 1 metal cations or ammonium. This is a crucial part of the solubility rules, as illustrated by the example of magnesium phosphate being 'generally insoluble,' except with group 1 metal cations.
💡Aqueous Phase
The aqueous phase refers to the state of being dissolved in water. In the video, the term is used to denote solubility, as in 'using the phase aq, aqueous which means that it dissolves in water.' It is a key term for understanding the outcome of solubility tests, as compounds that are soluble will be represented as being in the aqueous phase.
💡Exceptions
Exceptions in the context of the video refer to specific instances where the general solubility rules do not apply. The video discusses several exceptions, such as silver chloride and lead 2-sulfate, which are insoluble despite general rules suggesting they should be soluble. Understanding these exceptions is crucial for accurately predicting the solubility of compounds.
Highlights

Introduction to using solubility rules to determine if a compound is soluble or insoluble in water.

Group 1 metal ions like sodium, potassium, lithium, and rubidium are always soluble.

Ammonium and polyatomic ions like nitrate and acetate are always soluble.

Halides such as chloride, bromide, and iodide are generally soluble, with exceptions like silver and mercury.

Fluorides differ in solubility, having more exceptions compared to other halides.

Sulfates are generally soluble except with metals like calcium, barium, strontium, and lead.

Hydroxides are generally insoluble, but soluble when combined with group 1 metals or certain heavy group 2 alkaline earth metals.

Magnesium hydroxide is somewhat soluble, making it an exception among group 2 metals.

Sulfides, carbonates, phosphates, and chromates are generally insoluble unless paired with group 1 metal cations or ammonium.

Specific examples of soluble and insoluble compounds are discussed, such as sodium phosphate and potassium chloride.

Silver chloride is highlighted as an exception among chlorides, being insoluble.

The solubility of lead 2 nitrate is confirmed due to the always-soluble nature of nitrates.

The exceptions for sulfates are reiterated with lead 2-sulfate being insoluble.

Barium hydroxide's solubility is explained as an exception among hydroxides.

The video concludes with encouragement for viewers to practice determining solubility with additional compound examples.

Transcripts

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