How to Calculate Oxidation Number Practice Problems

Tyler DeWitt
16 Jun 201515:25
EducationalLearning
32 Likes 10 Comments

TLDRThis video tutorial effectively guides viewers through the process of determining oxidation numbers for elements in chemical compounds. It begins with basic examples and progressively tackles more complex problems, utilizing the periodic table and established rules for oxidation numbers. The video emphasizes the importance of the sum of oxidation numbers equaling zero for neutral compounds and provides clear explanations for calculating the oxidation numbers of various elements, including halogens, metals, and nonmetals, in different chemical contexts.

Takeaways
  • 📚 Understanding oxidation numbers is crucial for analyzing chemical compounds and their reactions.
  • 📈 Start with basic examples to build a strong foundation in determining oxidation numbers for elements in compounds.
  • 📊 Use the periodic table as a reference for specific rules related to the oxidation numbers of elements based on their groups.
  • 🔢 For neutral compounds, the sum of the oxidation numbers of all elements must equal zero.
  • 🌟 Recognize that elements like calcium and oxygen have common oxidation numbers (+2 for Ca, -2 for O) that can be used as a starting point.
  • 🧪 Apply knowledge of halogens and their typical oxidation numbers (-1), but be aware that they can vary depending on the compound.
  • 🔍 When no specific rule exists for an element, use the known oxidation numbers of other elements and the compound's neutrality to determine it.
  • 📐 Multiply the oxidation number by the number of atoms of that element present in the compound (e.g., for multiple halogens).
  • 🌐 Consider the charge of polyatomic ions when calculating the oxidation number of the central element.
  • 🔗 Understand that in compounds, elements like hydrogen typically have an oxidation number of +1 when bonded to nonmetals and -1 when bonded to metals.
  • 🌀 In complex scenarios where multiple halogens bond together, one may have a positive oxidation number while the other remains negative, balancing each other out.
Q & A

  • What is the oxidation number of calcium (Ca) in the compound CaO?

    -The oxidation number of calcium (Ca) in the compound CaO is +2, as it is a group 2A element and typically has an oxidation state of +2.

  • What is the general oxidation number for oxygen in compounds?

    -The general oxidation number for oxygen in compounds is -2, except in peroxides where it can be -1.

  • How do you determine the oxidation number of iodine (I) in the compound CaI2?

    -In the compound CaI2, the oxidation number of iodine (I) is -1 because it is a halogen and typically has an oxidation number of -1, except when paired with oxygen.

  • What rule is used to calculate the oxidation number of copper (Cu) in a neutral compound?

    -The rule used to calculate the oxidation number of copper (Cu) in a neutral compound is that the sum of oxidation numbers for a neutral compound should equal 0.

  • What is the oxidation number of iron (Fe) in the compound FeBr3?

    -The oxidation number of iron (Fe) in the compound FeBr3 is +3. This is determined by the fact that there are three bromine atoms each with an oxidation number of -1, and the sum of oxidation numbers must equal zero for a neutral compound.

  • How is the oxidation number of nitrogen (N) in NH4Cl determined?

    -The oxidation number of nitrogen (N) in NH4Cl is -3. This is found by considering the oxidation numbers of hydrogen (+1) and chlorine (-1) and using the fact that the sum of oxidation numbers in a neutral compound must be zero.

  • What is the oxidation number of carbon (C) in the polyatomic ion CO32-?

    -The oxidation number of carbon (C) in the polyatomic ion CO32- is +4. This is determined by the fact that the overall charge of the ion is -2, and there are three oxygen atoms each with an oxidation number of -2.

  • What is the oxidation number of barium (Ba) in the monatomic ion Ba2+?

    -The oxidation number of barium (Ba) in the monatomic ion Ba2+ is +2, as it is the same as its ion charge.

  • How is the oxidation number of phosphorus (P) in H2P2O7 determined?

    -The oxidation number of phosphorus (P) in H2P2O7 is +5. This is calculated by considering the oxidation numbers of hydrogen (+1) and oxygen (-2) and using the fact that the sum of oxidation numbers must equal the ion charge of -2 for the polyatomic ion.

  • What is the oxidation number of chlorine (Cl) in KClO3?

    -The oxidation number of chlorine (Cl) in KClO3 is +5. This is determined by considering the oxidation number of potassium (+1) and oxygen (-2) and using the fact that the sum of oxidation numbers must equal zero for a neutral compound.

  • How do halogens typically behave in terms of oxidation numbers when paired with other elements?

    -Halogens typically have an oxidation number of -1 when paired with non-oxygen elements. However, when paired with oxygen, their oxidation numbers can be positive, as seen with chlorine in KClO3, which has an oxidation number of +5.

  • What is the oxidation number of chlorine (Cl) in Ca(ClO)2?

    -The oxidation number of chlorine (Cl) in Ca(ClO)2 is +7. This is determined by considering the oxidation number of calcium (+2) and the fact that there are two oxygen atoms each with an oxidation number of -2, and the sum of oxidation numbers must equal zero for a neutral compound.

Outlines
00:00
📚 Introduction to Oxidation Numbers

This paragraph introduces the concept of oxidation numbers and explains the rules for determining them in chemical compounds. It emphasizes the importance of understanding these rules through a series of examples, starting with basic cases and progressing to more complex ones. The video script outlines the rules for elements like calcium (Ca) and oxygen (O), and how to apply these rules to calculate the oxidation numbers for other elements, such as iodine (I) and copper (Cu), in neutral compounds. The key takeaway is that the sum of oxidation numbers in a neutral compound must equal zero.

05:01
🧪 Calculation of Oxidation Numbers for Polyatomic Ions

This paragraph delves into the calculation of oxidation numbers for elements in polyatomic ions and compounds. It explains how to handle situations where there are no specific rules for certain elements by using the known oxidation numbers of other elements and the principle that the sum of oxidation numbers in a neutral compound must be zero. The paragraph covers compounds like NH4Cl, H2P2O7, and KClO3, highlighting the unique cases where elements like chlorine (Cl) and oxygen (O) deviate from their usual oxidation states. The explanation also includes the calculation for Ba+ and the oxidation number of phosphorus (P) in H2P2O7.

10:02
🌟 Advanced Examples with Halogens

This paragraph presents advanced examples involving halogens and their unique oxidation numbers in different compounds. It explains how the oxidation numbers of halogens can vary, especially when they are paired with other elements. The video script covers compounds like BeF5, where fluorine (F) always has an oxidation number of -1, and bromine (Br) takes on a positive oxidation number to balance the compound. The paragraph also discusses the calculation of oxidation numbers for compounds like Ca(ClO2), where the presence of parentheses indicates the repetition of a group of atoms, and how to adjust the calculations accordingly.

15:02
🎓 Summary and Final Thoughts

In the final paragraph, the video script wraps up the discussion on oxidation numbers, emphasizing the viewer's newfound comfort and understanding of the topic. The aim is to ensure that the viewer is well-equipped to determine oxidation numbers in various chemical compounds. The paragraph serves as a recap and encouragement for further exploration of chemical concepts related to oxidation numbers.

Mindmap
Keywords
💡Oxidation Numbers
Oxidation numbers are a system used to keep track of electrons in redox reactions. They are assigned to each atom in a compound and represent the charge an atom would have if all bonds were ionic. In the video, the main theme revolves around calculating oxidation numbers for elements in chemical compounds, using rules and examples to illustrate the process.
💡Neutral Compound
A neutral compound is a chemical species in which the sum of the oxidation numbers of all atoms equals zero, indicating that there is no overall charge. This concept is crucial in the video, as it is used to determine the oxidation numbers of elements that do not have predefined rules.
💡Periodic Table
The periodic table is a tabular arrangement of the chemical elements, ordered by their atomic number, electron configurations, and recurring chemical properties. It serves as a reference in the video for determining the oxidation numbers of elements based on their group and position.
💡Halogens
Halogens are a group of nonmetal elements in group 7a of the periodic table, including fluorine, chlorine, bromine, iodine, and astatine. They typically have oxidation numbers of -1 in compounds but can exhibit positive oxidation states when bonded to oxygen. Halogens are a key concept in the video, as their oxidation numbers vary depending on the compound they are in.
💡Polyatomic Ions
Polyatomic ions are charged species composed of two or more atoms covalently bonded together. They act as a single ion in chemical reactions and are treated as individual entities when determining oxidation numbers. The video explains how to calculate the oxidation numbers of elements within polyatomic ions, taking into account the overall charge of the ion.
💡Redox Reactions
Redox reactions, short for reduction-oxidation reactions, are chemical processes in which atoms or ions lose or gain electrons. The concept of oxidation numbers is directly related to redox reactions, as they help to track the transfer of electrons between species. The video's focus on oxidation numbers is a fundamental aspect of understanding redox reactions.
💡Group 1a Elements
Group 1a elements, also known as the alkali metals, are located in the first column of the periodic table. These elements typically have an oxidation number of +1 in their compounds. The video uses this rule to determine the oxidation number of sodium (Na) in NaBH4.
💡Group 2a Elements
Group 2a elements, also known as the alkaline earth metals, are found in the second column of the periodic table. These elements usually have an oxidation number of +2 in their compounds. The video uses this rule to determine the oxidation number of calcium (Ca) in CaO.
💡Peroxides
Peroxides are a class of compounds that contain the peroxide ion (O2^2−). In peroxides, oxygen has an oxidation number of -1, which is different from its usual -2 in other compounds. This distinction is important when calculating oxidation numbers in peroxides, as discussed in the video.
💡Ion Charge
The ion charge refers to the electrical charge of an atom or group of atoms that have lost or gained electrons. In the context of the video, understanding ion charges is essential for determining oxidation numbers, especially for polyatomic ions and monatomic ions.
💡Element by Itself
An element by itself refers to a pure substance that is made up of only one type of atom. When an element is not combined with any other elements, its oxidation number is zero. This concept is used in the video to determine the oxidation number of oxygen in O2.
Highlights

The video focuses on mastering the calculation of oxidation numbers for elements in chemical compounds through numerous examples.

The rules for determining oxidation numbers are explained, with a periodic table used as a reference.

Calcium (Ca) from group 2A always has an oxidation number of +2.

Oxygen typically has an oxidation number of -2, except in peroxides.

The sum of oxidation numbers in a neutral compound must equal zero.

Iodine (I), being a halogen, usually has an oxidation number of -1, but it is +1 in the compound CaI.

For the compound FeBr3, the oxidation number of iron (Fe) is +3, calculated by balancing the -3 from three bromine atoms.

In NH4Cl, nitrogen's oxidation number is -3, derived from the known oxidation numbers of hydrogen and chlorine.

Carbon's oxidation number in the carbonate ion (CO3^2-) is +4, calculated by balancing the -2 from three oxygen atoms against the ion's charge.

Barium (Ba) as a monatomic ion has an oxidation number equal to its charge, which is +2.

In H2P2O7, phosphorus' oxidation number is +5, determined by balancing the overall charge of the compound.

Oxygen in its elemental form has an oxidation number of 0.

In KClO3, chlorine's oxidation number is +5, calculated by balancing the oxidation numbers with potassium and oxygen.

In H2O2, hydrogen has an oxidation number of +1 and oxygen has a rare oxidation number of -1 due to it being a peroxide.

Sodium (Na) in NaBH4 has an oxidation number of +1, while boron's oxidation number is +3 to balance the compound.

In BrF5, bromine has an oxidation number of +5 to balance the -1 oxidation number of five fluorine atoms.

Calcium (Ca) maintains an oxidation number of +2 in Ca(ClO)2, and chlorine's oxidation number is +7 when paired with two oxygen atoms.

The video aims to make viewers comfortable with calculating oxidation numbers, showcasing a variety of compounds and scenarios.

Transcripts

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Chemistry EducationOxidation NumbersPeriodic TableChemical CompoundsTeaching VideoElement RulesNeutral CompoundsHalogensPolyatomic Ions