01:160:163 Lecture Notes - Lecture 27: Oxidation State, Electronegativity, Hydronium

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aquamarinetiger679

19 May 2016

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Document Summary

Oxidation number: the charge an atom would have if it were to completely surrender the electron to the most electronegative atom. An element in its elemental (standard) form has an oxidation number of zero. The total charge of each compound has to equal the charge sum of the compound"s parts. Assign the species that have known and reliable oxidation numbers first, then move on to the others to complete the total charge of the compound. Comproportionation reaction: one product is formed when a single element in two separate compounds under goes both oxidation and reduction. On the other side of the rxn to balance the h2o. Then balance the charge with e- (electrons) Bring the two equations back together again. If there is double of one half reaction, multiply the other half by two to make the whole reaction equal. Galvanic cells: (voltaic cell) uses spontaneous redox rxn to generate electric energy.

Related Questions

Oxidation Numbers

The oxidation number of an element is the "charge" the element would have if all of its bonds were completely ionic; that is, if the electron pairs of each bond were transferred to the more electronegative atom.

For monatomic ions the oxidation number is simply the charge of the ion. For covalently bonded elements the oxidation number is a bookkeeping device and does not mean that the element carries an actual charge.

Determine the oxidation state for each of the elements below.

The oxidation state of chlorine in hypochlorite ion ClO- is______
The oxidation state of chlorine in chlorine pentafluoride ClF5 is_____
The oxidation state of sulfur in sulfur dioxide SO2 is_______

Oxidation states are important for keeping track of electrons in oxidation-reduction reactions. Here are some general rules to remember:

In most cases, oxygen has an oxidation state of ?2.
Group 1 and group 2 elements on the periodic table have +1 and +2 oxidation states, respectively.
In most cases, hydrogen has an oxidation state of +1.
Many elements can have more than one oxidation state. In such cases, use the other elements in the compound whose oxidation states are known to determine the oxidation state of the element that varies.

Neutral compounds

In a neutral compound, the sum of the oxidation states is zero. Note that the sign of the oxidation states and the number of atoms associated with each oxidation state must be considered. In H2O, for example, each hydrogen atom has an oxidation state of +1 and each oxygen atom has an oxidation state of ?2 for a total of 2(+1)+(?2)=0.

Part A

What is the oxidation state of an individual carbon atom in CaCO3?

Express the oxidation state numerically (e.g., +1).

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Part B

What is the oxidation state of an individual nitrogen atom in HNO3?

Express the oxidation state numerically (e.g., +1).

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Ions

In an ion, the sum of the oxidation states is equal to the overall ionic charge. Note that the sign of the oxidation states and the number of atoms associated with each oxidation state must be considered. In OH?, for example, the oxygen atom has an oxidation state of ?2 and the hydrogen atom has an oxidation state of +1, for a total of (?2)+(+1)=?1.

Part C

What is the oxidation state of an individual sulfur atom in SO32??

Express the oxidation state numerically (e.g., +1).

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Part D

What is the oxidation state of each individual carbon atom in C2O42??

Express the oxidation state numerically (e.g., +1).

Predict the charge that an aluminum ion would have.