Question

What is the oxidation state of \(\mathrm{Cr}\) in each compound? a. \(\mathrm{CrO}\) b. \(\mathrm{CrO}_{3}\) c. \(\mathrm{Cr}_{2} \mathrm{O}_{3}\)

Short answer

The oxidation states of Cr in the compounds are as follows: a. +2 in CrO, b. +6 in CrO3, c. +3 in Cr2O3.

Step-by-step solution

Identifying the known oxidation states

The oxidation state of oxygen is typically -2 in compounds (except in peroxides or when bonded to fluorine).

Calculating the oxidation state for CrO

Let the oxidation state of Cr be x. In CrO, the compound is neutral, so the sum of oxidation states is zero: x + (-2) = 0. Solve for x to find the oxidation state of Cr.

Calculating the oxidation state for CrO3

Let the oxidation state of Cr be x. In CrO3, the sum of oxidation states is zero: x + 3(-2) = 0. Solve for x to find the oxidation state of Cr.

Calculating the oxidation state for Cr2O3

Let the oxidation state of Cr be x. In Cr2O3, the total charge is zero, and there are two Cr atoms, so the sum of oxidation states is zero: 2x + 3(-2) = 0. Solve for x to find the oxidation state of Cr.

Key concepts

Redox Chemistry

Redox chemistry is a fundamental concept in chemistry that revolves around the processes of reduction and oxidation. It is through redox reactions that substances engage in electron transfer, which is crucial for forming and breaking chemical bonds. To envision this, think about a dance of electrons where some elements 'give away' electrons, while others 'take' them. This electron exchange not only changes the oxidation state of the elements involved but also alters the properties of the substances.

An excellent example of a redox reaction is the formation of water from hydrogen and oxygen. The hydrogen atoms (the electron donors) are oxidized, and the oxygen atoms (the electron acceptors) are reduced, leading to a stable compound. Understanding redox chemistry is not only vital in a laboratory setting but also in everyday life, as it governs the principles behind batteries, combustion engines, and even biological processes like cellular respiration.

Chemical Compounds

Chemical compounds are substances formed by the chemical combination of two or more elements in specific ratios and with distinct properties. The formation of compounds involves the making and breaking of chemical bonds, which are the result of interactions between the valence electrons of the combining atoms. These bonds can be ionic, where electrons are transferred, or covalent, where electrons are shared.

Lets break it down - imagine atoms as individuals who can form 'friendships' (bonds) by either lending, borrowing, or equally sharing 'items' (electrons). It's these 'friendships' that dictate the characteristics of the resulting compounds. Think about water again; it is a compound where hydrogen and oxygen share electrons through covalent bonding, giving it unique properties different from its constituent elements. Understanding the various ways atoms can combine and form compounds is crucial in predicting how substances will behave and interact in different environments.

Oxidation Numbers

Oxidation numbers, also known as oxidation states, serve as a bookkeeping tool in chemistry to keep track of electron transfer in redox reactions. Each atom in a compound has an oxidation number that helps determine how many electrons are lost or gained during a reaction. In simple ions, the oxidation number is equal to the charge of the ion, but in covalent compounds, oxidation numbers are assigned by following certain rules.

For instance, oxidation numbers can tell us who's the electron donor and acceptor in a redox reaction. Oxygen typically has an oxidation number of -2, except when it forms compounds with fluorine or in peroxides. In the context of our exercise, identifying the known oxidation states for oxygen allowed for the calculation of the oxidation state of chromium in different compounds by setting up algebraic equations that satisfy the overall neutrality of the compounds. Understanding and assigning proper oxidation numbers is essential for balancing redox equations, predicting reaction products, and even in fields such as electrochemistry and metallurgy.