ALEKS: Writing net ionic equations

Roxi Hulet
8 Jul 202307:19
EducationalLearning
32 Likes 10 Comments

TLDRThis instructional video demonstrates the process of converting a molecular equation into a net ionic equation, essential for understanding chemical reactions in aqueous solutions. The presenter emphasizes the importance of having a periodic table and a polyatomic ion table for reference. The tutorial guides viewers through identifying and separating polyatomic ions, predicting ion charges, and simplifying the equation by canceling out ions that do not change during the reaction, resulting in a clear net ionic equation.

Takeaways
  • 📚 To solve the Alex problem of writing net ionic equations, a periodic table and a table of polyatomic ions are essential tools.
  • 🔍 The first step is to break apart all reactants and products in the aqueous phase into their cations and anions.
  • 🧩 When a compound contains three or more different types of atoms, it likely contains a polyatomic ion.
  • 🔎 Use the table of polyatomic ions to identify the specific polyatomic ion present in the compound, such as \( \text{SO}_4^{2-} \).
  • ⚖️ The charge of the cation can be predicted based on the charge of the polyatomic ion present in the compound.
  • 📉 For compounds with only two different types of atoms, they are simple ionic compounds and do not contain polyatomic ions.
  • 🔑 Elements in the first column of the periodic table typically form \( +1 \) ions, and those in the next column form \( +2 \) ions.
  • 🌐 Transition metals have variable charges that cannot be easily predicted by their position on the periodic table.
  • 📝 In writing the net ionic equation, include the states of the substances to indicate whether they are aqueous or not.
  • 🚫 Solid state substances like \( \text{S} \) do not need to be broken apart in the net ionic equation.
  • ✂️ Convert the total ionic equation to a net ionic equation by canceling out ions that appear on both sides and are not undergoing a chemical change.
Q & A

  • What is the main topic of the video?

    -The video is about solving the 'Alex problem', which involves writing net ionic equations.

  • What tools are recommended to have handy while solving the problem?

    -A periodic table and a table of polyatomic ions are recommended, with the latter available on socratic.org.

  • What is the first step in converting a molecular equation into a net ionic equation?

    -The first step is to break apart all reactants and products that are in the aqueous phase into their cations and anions.

  • Why is the periodic table useful in this process?

    -The periodic table is useful for identifying the charges of cations and anions, especially when dealing with polyatomic ions.

  • What does it mean if a compound contains three or more different types of atoms?

    -If a compound contains three or more different types of atoms, it likely contains a polyatomic ion.

  • How can you predict the charge of a cation in a compound?

    -You can predict the charge of a cation by balancing it with the charge of the anion in the compound, ensuring the overall charge is neutral.

  • What is the role of the polyatomic ion in the compound discussed in the video?

    -The polyatomic ion in the compound discussed is \( ext{SO}_4^{2-} \), which helps determine the charge of the cation.

  • Why is it important to include the state of the substances in the equation?

    -Including the state (e.g., aqueous) is crucial as it indicates the form in which the substances exist and react, affecting how they are written in the equation.

  • What is the difference between a total ionic equation and a net ionic equation?

    -A total ionic equation includes all the ions present, while a net ionic equation only includes the ions that actually change during the reaction, omitting those that appear on both sides.

  • How do you determine which ions to cancel out in a net ionic equation?

    -You cancel out ions that appear on both the reactant and product sides of the equation and do not undergo any chemical change.

Outlines
00:00
🧪 Introduction to Writing Net Ionic Equations

This paragraph introduces the process of converting molecular equations into net ionic equations, emphasizing the need for a periodic table and a table of polyatomic ions. The speaker explains the initial step of breaking apart substances in the aqueous phase into their constituent cations and anions, using the periodic table to identify polyatomic ions. The example given involves a compound with tin, sulfur, and oxygen, where the presence of three different types of atoms indicates a polyatomic ion. The sulfate ion (SO4^2-) is identified, and the tin cation is predicted to have a +2 charge to balance the charges in the compound.

05:00
🔍 Transition to Net Ionic Equations and Charge Prediction

The second paragraph continues the explanation of writing net ionic equations, focusing on the transition from total ionic equations. The speaker demonstrates how to identify and cancel out ions that are present on both sides of the equation and do not undergo any chemical change. This process simplifies the equation to show only the ions that are involved in the reaction. The example provided involves potassium sulfide (K2S) and tin sulfate, where the charges of the potassium and sulfide ions are predicted using the periodic table. The final step is to cancel out the common ions, resulting in the net ionic equation, which shows the actual chemical change occurring.

Mindmap
Keywords
💡Net Ionic Equations
Net ionic equations are a simplified form of chemical equations that show only the substances that actually change during a reaction, omitting those that remain the same. In the context of the video, they are essential for understanding how to break down complex chemical reactions into their fundamental components, focusing on the ions that are involved in the reaction. The script provides a step-by-step process to derive a net ionic equation from a molecular equation, highlighting its importance in solving the 'Alex problem'.
💡Periodic Table
The periodic table is a tabular arrangement of the chemical elements, ordered by their atomic number, electron configuration, and recurring chemical properties. In the video, the periodic table is used to determine the charges of ions, especially for elements in predictable columns, which helps in predicting the charges of cations like potassium and anions like sulfide.
💡Polyatomic Ions
Polyatomic ions are groups of atoms that are covalently bonded and have a net charge. They are important in the script as they are part of the reactants and products in the chemical reaction being discussed. The table of polyatomic ions is used to identify and predict the charge of these ions, such as the sulfate ion (SO4^2-), which is crucial for balancing the charges in the net ionic equation.
💡Aqueous Phase
The aqueous phase refers to the state of substances when they are dissolved in water. In the script, the aqueous phase is significant because it dictates which substances need to be broken down into their constituent ions. The video explains that all reactants and some products in the aqueous phase must be dissociated into ions for the net ionic equation.
💡Cations
Cations are positively charged ions that result from the loss of electrons from an atom. The video script uses the periodic table to determine the charges of cations, such as the tin ion (Sn^2+), which is crucial for balancing the charges in the reaction and writing the correct net ionic equation.
💡Anions
Anions are negatively charged ions that result from the gain of electrons by an atom. The script discusses anions like the sulfate ion (SO4^2-) and the sulfide ion (S^2-), which are part of the reactants and products. Understanding anions is essential for correctly writing the net ionic equation and balancing the charges.
💡Molecular Equation
A molecular equation is a chemical equation that includes the formulas of all reactants and products as they are written, without dissociating them into ions. The script starts with a molecular equation and then explains the process of converting it into a net ionic equation by breaking down the substances in the aqueous phase.
💡Charge Balance
Charge balance is the principle that the total positive charge must equal the total negative charge in a chemical equation. The video emphasizes the importance of charge balance when determining the charges of ions, ensuring that the equation is electrically neutral, which is a fundamental aspect of writing net ionic equations.
💡Ionic Compounds
Ionic compounds are formed by the electrostatic attraction between cations and anions. The script distinguishes ionic compounds from molecular compounds by the number of different types of atoms they contain. For example, potassium sulfide (K2S) is an ionic compound with predictable charges for potassium and sulfide ions.
💡Transition Metals
Transition metals are a group of elements in the periodic table known for their ability to form a variety of oxidation states. The script mentions that the charges of transition metal ions cannot be easily predicted by their position on the periodic table, unlike other elements that form ions with predictable charges.
💡Total Ionic Equation
A total ionic equation is an intermediate step in the process of writing a net ionic equation. It includes all the ions from the dissociation of the reactants and products in the aqueous phase. The script explains that a total ionic equation is not the final goal but must be simplified further to remove ions that do not change during the reaction, resulting in the net ionic equation.
Highlights

The video explains how to solve the Alex problem called writing net ionic equations.

A periodic table and a table of polyatomic ions are recommended for solving the problem.

The table of polyatomic ions can be found on socratic.org.

The first step is to break apart all reactants and products in the aqueous phase into their cations and anions.

The periodic table is useful for identifying polyatomic ions in molecular formulas.

Polyatomic ions stay together and can be identified by having three or more different types of atoms.

The sulfate ion, SO4, is an example of a polyatomic ion with a 2- charge.

Cations and anions must balance each other's charges in a compound.

Predicting the charge of cations can be done using the periodic table.

Elements in the first column of the periodic table form +1 ions.

Elements in the second column form +2 ions, and so on for predictable charges.

Transition metals have variable charges that are not easily predictable from their position on the periodic table.

The potassium ion (K+) has a +1 charge, and there are two of them in the compound K2S.

The sulfide ion (S2-) has a -2 charge, as indicated by its position on the periodic table.

Solid-state substances like SnS are not altered in the net ionic equation.

The final product, K2SO4, must be broken down into its cation and anion if it is in the aqueous phase.

The net ionic equation is derived by canceling out ions that are present on both sides of the equation and do not undergo change.

The final step is to clean up the equation by erasing the canceled ions to present the net ionic equation.

Transcripts

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Chemistry TutorialNet Ionic EquationsPeriodic TablePolyatomic IonsAqueous SolutionsIonic CompoundsSulfate IonPotassium IonChemical ReactionsEducational ContentScience Learning