ch 11 - Oxidation-Reduction Reactions Flashcards Preview

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Flashcards in ch 11 - Oxidation-Reduction Reactions Deck (21)
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1

oxidation-reduction reactions (redox)

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

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oxidation

loss of electrons

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reduction

gain of electrons

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oxidizing agent

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

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reducing agent

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

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characteristics of oxidizing agents

almost all contain oxygen or another strongly electronegative element

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characteristics of reducing agents

often contain metal ions or hydrides (H-)

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common oxidizing agents

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

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common reducing agents

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

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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

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formal charge

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

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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)

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spectator ions

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

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net ionic equation

shows only species that actually participate in a reaction

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combustion reactions

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

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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

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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

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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

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what species are involved in net ionic equations

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

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what is the oxidation number of any free element

0

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what is the oxidation number of any free diatomic species

0