ch 11 - Oxidation-Reduction Reactions Flashcards Preview

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oxidation-reduction reactions (redox)

reactions that involve transfer of electrons from one chemical species to another



loss of electrons



gain of electrons


oxidizing agent

causes another atom in redox to become oxidized and is itself reduced


reducing agent

causes another atom in redox to become reduced and is itself oxidized


characteristics of oxidizing agents

almost all contain oxygen or another strongly electronegative element


characteristics of reducing agents

often contain metal ions or hydrides (H-)


common oxidizing agents

O2, H2O2, F2, Cl2, Br2, I2, H2SO4, HNO3, NaClO, KMnO4, CrO3, Na2Cr2O7, Pyridinium chlorochromate (PCC), NAD+, FADH


common reducing agents

CO, C, B2H6, Sn2+ and other pure metals, Hydrazine, Zn(Hg), Lindlar's catalyst, NaBH4, LiAlH4, NADH, FADH2


rules for assigning oxidation number

1. oxidation number of a free element is zero (N2, P4, S8); 2. the oxidation number for a monatomic ion is equal to the charge of the ion (Na+ = +1); 3. the oxidation number of each Group IA element in a compound is +1; 4. the oxidation number of each Group IIA element in a compound is +2; 5. number in Group VIIA elements in compound is -1, except when combined with an element of higher electronegativity; 6. number of hydrogen is usually +1 but is -1 in compounds with less electronegative elements (Groups IA and IIA); 7. in most compounds, the oxidation number of oxygen is -2 with exception of peroxides (-1) and compounds with more electronegative elements; 8. sum of ox numbers of all atoms present in a neutral compound is zero; sum of ox numbers all all atoms in polyatomic ion = charge of ion


formal charge

gives one electron to each atom in a bond where oxidation number gives all to more electronegative atom


half-reaction method

also called ion-electron method; method for balancing redox equations in which equation is separated into two half-reactions (oxidation part and reduction part)


spectator ions

an ion that does not take part in the overall reaction but remains in the solution unchanged


net ionic equation

shows only species that actually participate in a reaction


combustion reactions

a fuel (usually a hydrocarbon) is mixed with an oxidant (usually oxygen), forming carbon dioxide and water


disproportionation (or dismutation) reactions

specific type of redox reaction in which an element undergoes both oxidation and reduction in producing its products; usually accomplished by enzymes


oxidation-reduction titrations

follow the charge (as electrons) transfer in a reaction in order to reach the equivalence point; can utilize indicators that change color at a particular voltage (emf) value


Potentiometric titration

a form of redox titration where no indicator is used; electrical potential difference (voltage) is measured using a voltmeter; voltage changes as redox titration progresses


what species are involved in net ionic equations

all species that are not aqueous and those species that make up the non-aqueous species


what is the oxidation number of any free element



what is the oxidation number of any free diatomic species