Course Hero Logo

4 al s 3 o 2 g 2 al 2 o 3 s the term reduction

Course Hero uses AI to attempt to automatically extract content from documents to surface to you and others so you can study better, e.g., in search results, to enrich docs, and more. This preview shows page 203 - 206 out of 295 pages.

4 Al(s)+3 O2(g)2Al2O3(s)The term reduction originally referred to the decrease in mass observed when a metal oxide was heatedwith a substance such as hydrogen gas in a process used to extract metals from ores. When solid copper(I)oxide is heated with hydrogen, for example, the mass of the original sample decreases, or isreduced,because pure copper forms andoxygen atoms are lostin the form of water vapor.Cu2O(s)+H2(g)2 Cu(s)+H2O(g)In modern chemistry, the termoxidationhas been broadened to include any process by which an atomloses electrons. Similarly, the termreductionnow refers to any process by which an atom gains electrons.An oxidation-reduction reaction, or aredoxreaction, is one in which there is gain or loss of electrons inone or more of the reactants.Identifying gains and losses of electrons begins with theoxidation stateof each atom in a chemicalreaction. The oxidation state is the “charge” that an atom appears to have when in a compound. The rulesfor assigning oxidation states are as follows:1.Atoms in substances containing only one element have a zero oxidation state.H2, N2, O2, O3, P4, and S8contain atoms with zero oxidation states.2.Monatomic ions have an oxidation state that is the same as their charge.Fhas an oxidation state of −1. O2−has an oxidation state of −2.
[Type here]203Montgomery CollegeCC BY-NC-SA-4.0Spring 20193.First assign an oxidation state to each hydrogen atom and then to each oxygen atom. Then continuewith the other atoms in the compound.(a)Hydrogen has an oxidation state of +1 when combined with a nonmetal.In the compound HF, the hydrogen atom has an oxidation state of +1. Fluoride has an oxidationstate of −1.(b)Oxygen almost always has an oxidation state of2.In the compound H2O, each hydrogen atom has an oxidation state of +1 and the oxygen atomhas an oxidation state of −2.One exception is hydrogen peroxide, H2O2, in which each hydrogen atom has an oxidation stateof +1 and each oxygen atom has an oxidation state of −1.4.The sum of the oxidation states of a species must equal the overall charge of that species.Carbon dioxide, CO2, has two oxygen atoms, each with an oxidation state of −2. In order to havea neutral molecule, the oxidation state of carbon must be +4.Chromate, CrO42−, contains four oxygen atoms, each with an oxidation state of −2 for a total of−8. Chromium must therefore have an oxidation state of +6. When added, these leave −2 for theoverall charge of the ion.Example 7.Assign an oxidation state toeachatom in the following compounds.(a) carbon monoxide(b) iron(III) sulfate(c) zinc chlorideSolutions(a) CO is a neutral molecule. The oxygen has anoxidation state of −2 and the carbon has an oxidationstate of +2.
[Type here]204Montgomery CollegeCC BY-NC-SA-4.0Spring 2019(b) Fe2(SO4)3is a neutral compound. The name of the compound states that iron has an oxidation state of+3. Oxygen has an oxidation state of −2. The oxidation state for the three sulfur atoms must bedetermined.Two iron atoms give a total of +6. Twelve oxygen atoms give a total of −24. Thecompound is neutral, so the total must be zero. Let x = total sulfur charge:iron + oxygen + sulfur = 02(+3) + 12(−2) + x = 0x = +18There are three sulfur atoms in the compound, so each must have a charge of +18/3 = +6.

Upload your study docs or become a

Course Hero member to access this document

Upload your study docs or become a

Course Hero member to access this document

End of preview. Want to read all 295 pages?

Upload your study docs or become a

Course Hero member to access this document

Term
Spring
Professor
Staff
Tags
Chemistry, Orders of magnitude, OpenStax Chemistry

Newly uploaded documents

Show More

Newly uploaded documents

Show More

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture