Chapter 5: Problem 29
Assign oxidation numbers to the atoms in the following: (a) \(\mathrm{ClO}_{4}^{-},\) (b) \(\mathrm{Cl}^{-}\), (c) \(\mathrm{SF}_{6}\), and (d) \(\mathrm{Au}\left(\mathrm{NO}_{3}\right)_{3}\).
Short Answer
Expert verified
The oxidation numbers for the respective elements are: (a) Cl: +7, O: -2; (b) Cl: -1; (c) S: +6, F: -1; (d) Au: +3, N: +5, O: -2.
Step by step solution
01
Understanding Oxidation Numbers
Oxidation numbers (or states) are assigned to atoms to keep track of electron transfer in redox reactions. The rules for assigning oxidation states include: (1) the oxidation state of a free element is zero, (2) for monoatomic ions, the oxidation state is equal to the charge of the ion, (3) hydrogen has an oxidation state of +1 (except in hydrides where it's -1), (4) oxygen usually has an oxidation state of -2 (except in peroxides or when bonded to fluorine), and (5) the sum of all oxidation states in a neutral compound must be zero, while in a polyatomic ion, it must equal the ion's charge.
02
Assigning Oxidation Number to Cl in \(\mathrm{ClO}_{4}^{-}\)
Start by applying the rules: oxygen has an oxidation number of -2. In \(\mathrm{ClO}_{4}^{-}\), there are four oxygens, giving a total of -8. Because the ion has a charge of -1, the oxidation number of chlorine must be such that the sum of the oxidation numbers equals -1. Let the oxidation number of Cl be x. The equation is x + 4(-2) = -1, which simplifies to x - 8 = -1. Solving for x gives x = +7.
03
Assigning Oxidation Number to Cl in \(\mathrm{Cl}^{-}\)
For the monoatomic ion \(\mathrm{Cl}^{-}\), the oxidation number is equal to the charge of the ion. Therefore, the oxidation number of Cl is -1.
04
Assigning Oxidation Numbers in \(\mathrm{SF}_{6}\)
For the molecule \(\mathrm{SF}_{6}\), sulfur (S) is bonded to six fluorine (F) atoms. Fluorine has a fixed oxidation number of -1 in all its compounds. So, the total for the six fluorine atoms is -6. As \(\mathrm{SF}_{6}\) is a neutral molecule, the sum of oxidation numbers must equal zero. If we let x be the oxidation number of S, the equation becomes x + 6(-1) = 0. Solving for x gives x = +6.
05
Assigning Oxidation Numbers in \(\mathrm{Au}\left(\mathrm{NO}_{3}\right)_{3}\)
In \(\mathrm{Au}\left(\mathrm{NO}_{3}\right)_{3}\), start with the nitrate ion \(\mathrm{NO}_{3}^{-}\). Oxygen has an oxidation number of -2, giving a total of -6 for the three oxygen atoms. The ion has an overall charge of -1. Let the oxidation number of nitrogen (N) be a. The equation is a + 3(-2) = -1, which simplifies to a - 6 = -1, giving a = +5. Since there are 3 nitrate ions attached to Au, the overall charge contributed by the nitrates is -3. Gold (Au) in this compound must balance this with a +3 oxidation state.
Unlock Step-by-Step Solutions & Ace Your Exams!
-
Full Textbook Solutions
Get detailed explanations and key concepts
-
Unlimited Al creation
Al flashcards, explanations, exams and more...
-
Ads-free access
To over 500 millions flashcards
-
Money-back guarantee
We refund you if you fail your exam.
Over 30 million students worldwide already upgrade their learning with Vaia!
Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Oxidation States
When we talk about oxidation states (also known as oxidation numbers), we're referring to a concept that is fundamental to understanding chemical reactions, especially redox reactions. An oxidation state is a number that represents the total number of electrons an atom either gains or loses to form a chemical bond. Learning to assign these numbers correctly is crucial for students as it allows them to keep track of electrons during the process of oxidation and reduction.
In order to assign oxidation states, several rules have been established. These include that the oxidation state of a pure element is always zero and the oxidation state for a monoatomic ion equals its charge. Hydrogen typically has an oxidation number of +1, except when it forms hydrides with metals, in which case it is -1. Oxygen generally has an oxidation state of -2, unless it's in peroxides or bonded to fluorine. Remember, these guidelines are not without exceptions, so getting familiar with them is key. Moreover, the algebraic sum of the oxidation states in a molecule must be zero, while for a polyatomic ion, it must equal the overall charge of the ion.
In order to assign oxidation states, several rules have been established. These include that the oxidation state of a pure element is always zero and the oxidation state for a monoatomic ion equals its charge. Hydrogen typically has an oxidation number of +1, except when it forms hydrides with metals, in which case it is -1. Oxygen generally has an oxidation state of -2, unless it's in peroxides or bonded to fluorine. Remember, these guidelines are not without exceptions, so getting familiar with them is key. Moreover, the algebraic sum of the oxidation states in a molecule must be zero, while for a polyatomic ion, it must equal the overall charge of the ion.
Redox Reactions
Redox reactions are types of chemical reactions that involve the transfer of electrons between two species. The term 'redox' is a shorthand for 'reduction-oxidation' reactions. In these processes, one species will lose electrons and become oxidized while another gains electrons and becomes reduced. Assigning oxidation numbers is an essential step in identifying the elements that get oxidized and reduced during a redox reaction.
Redox reactions are everywhere—from cellular respiration in the human body that helps convert food into energy to industrial processes like the extraction of metals from ores. The concept empowers students to balance chemical equations for redox reactions, predict the outcome of chemical processes, and understand how electrons move during chemical transformations. An increased grasp of oxidation states leads to a deeper comprehension of redox reaction mechanisms and the roles different elements play within them.
Redox reactions are everywhere—from cellular respiration in the human body that helps convert food into energy to industrial processes like the extraction of metals from ores. The concept empowers students to balance chemical equations for redox reactions, predict the outcome of chemical processes, and understand how electrons move during chemical transformations. An increased grasp of oxidation states leads to a deeper comprehension of redox reaction mechanisms and the roles different elements play within them.
Polyatomic Ions
Polyatomic ions are charged entities consisting of two or more atoms covalently bonded together or of a metal complex that can be considered as acting as a single unit. Common examples include sulfate (SO_4^{2-}), nitrate (NO_3^{-}), and ammonium (NH_4^{+}). In the context of assigning oxidation numbers, it's important to treat polyatomic ions as a cohesive group, where the sum of the oxidation numbers equals the ion's overall charge.
Understanding how to deal with these ions in terms of their electron count and distribution is fundamental for students because polyatomic ions often form the basis of more complex compounds. Students must account for the oxidation states of all atoms within the ion, balancing them against the total charge to maintain electrical neutrality.
Understanding how to deal with these ions in terms of their electron count and distribution is fundamental for students because polyatomic ions often form the basis of more complex compounds. Students must account for the oxidation states of all atoms within the ion, balancing them against the total charge to maintain electrical neutrality.
Chemical Compounds
Chemical compounds are substances composed of two or more different types of elements, which are held together by chemical bonds. These can be simple, like water (H_2O), or complex, like glucose (C_6H_{12}O_6). When assigning oxidation numbers in a compound, the goal is to use the aforementioned rules systematically to determine the electron count for each element.
With chemical compounds, it is essential to differentiate between ionic and covalent bonds, as this will influence the oxidation states. In ionic compounds, atoms are typically assigned oxidation numbers corresponding to the charges they would have if the compound was composed of ions. However, in covalent compounds, the electrons are shared between atoms, and we often assign oxidation numbers based on electronegativity differences. A solid grasp of how these numbers are allocated allows students not only to predict the behavior of elements in chemical reactions but also to understand the molecular structure and properties of the compounds in question.
With chemical compounds, it is essential to differentiate between ionic and covalent bonds, as this will influence the oxidation states. In ionic compounds, atoms are typically assigned oxidation numbers corresponding to the charges they would have if the compound was composed of ions. However, in covalent compounds, the electrons are shared between atoms, and we often assign oxidation numbers based on electronegativity differences. A solid grasp of how these numbers are allocated allows students not only to predict the behavior of elements in chemical reactions but also to understand the molecular structure and properties of the compounds in question.