ch 11 - Oxidation-Reduction Reactions

Question 1

oxidation-reduction reactions (redox)

Answer 1

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

Question 2

oxidation

Answer 2

loss of electrons

Question 3

reduction

Answer 3

gain of electrons

Question 4

oxidizing agent

Answer 4

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

Question 5

reducing agent

Answer 5

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

Question 6

characteristics of oxidizing agents

Answer 6

almost all contain oxygen or another strongly electronegative element

Question 7

characteristics of reducing agents

Answer 7

often contain metal ions or hydrides (H-)

Question 8

common oxidizing agents

Answer 8

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

Question 9

common reducing agents

Answer 9

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

Question 10

rules for assigning oxidation number

Answer 10

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

Question 11

formal charge

Answer 11

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

Question 12

half-reaction method

Answer 12

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

Question 13

spectator ions

Answer 13

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

Question 14

net ionic equation

Answer 14

shows only species that actually participate in a reaction

Question 15

combustion reactions

Answer 15

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

Question 16

disproportionation (or dismutation) reactions

Answer 16

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

Question 17

oxidation-reduction titrations

Answer 17

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

Question 18

Potentiometric titration

Answer 18

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

Question 19

what species are involved in net ionic equations

Answer 19

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

Question 20

what is the oxidation number of any free element

Answer 20

0

Question 21

what is the oxidation number of any free diatomic species

Answer 21

0