bài giảng hóa học bằng tiếng anh Redox Reaction hay nhất

Redox Reaction • one or more elements change oxidation number all single displacement, and combustion, some synthesis and decomposition • always have both oxidation and reduction spli

Redox Reaction

Redox Reaction

• one or more elements change oxidation number

all single displacement, and combustion,

some synthesis and decomposition

• always have both oxidation and reduction

split reaction into oxidation half-reaction and a

reduction half-reaction

• aka electron transfer reactions

half-reactions include electrons

• oxidizing agent is reactant molecule that causes oxidation

contains element reduced

• reducing agent is reactant molecule that causes reduction

contains the element oxidized

Oxidation & Reduction

• oxidation is the process that occurs when

oxidation number of an element increases

element loses electrons

compound adds oxygen

compound loses hydrogen

half-reaction has electrons as products

• reduction is the process that occurs when

oxidation number of an element decreases

element gains electrons

compound loses oxygen

compound gains hydrogen

half-reactions have electrons as reactants

Rules for Assigning Oxidation States

• rules are in order of priority

1 free elements have an oxidation state = 0

 Na = 0 and Cl2 = 0 in 2 Na(s) + Cl2(g)

2 monatomic ions have an oxidation state equal

to their charge

 Na = +1 and Cl = -1 in NaCl

3 (a) the sum of the oxidation states of all the

atoms in a compound is 0

 Na = +1 and Cl = -1 in NaCl, (+1) + (-1) = 0

Rules for Assigning Oxidation States

3. (b) the sum of the oxidation states of all the atoms in

a polyatomic ion equals the charge on the ion

 N = +5 and O = -2 in NO3– , (+5) + 3(-2) = -1

4. (a) Group I metals have an oxidation state of +1 in all

their compounds

 Na = +1 in NaCl

4. (b) Group II metals have an oxidation state of +2 in

all their compounds

 Mg = +2 in MgCl2

Rules for Assigning Oxidation States

5 in their compounds, nonmetals have oxidation

states according to the table below

 nonmetals higher on the table take priority

Nonmetal Oxidation State Example

Oxidation and Reduction

• oxidation occurs when an atom’s oxidation state increases during a reaction

• reduction occurs when an atom’s oxidation state decreases during a reaction

CH4 + 2 O2 → CO2 + 2 H2O

-4 +1 0 +4 –2 +1 -2

oxidation

reduction

Oxidation–Reduction

• oxidation and reduction must occur simultaneously

 if an atom loses electrons another atom must take them

• the reactant that reduces an element in another reactant

is called the reducing agent

 the reducing agent contains the element that is oxidized

• the reactant that oxidizes an element in another reactant

is called the oxidizing agent

 the oxidizing agent contains the element that is reduced

2 Na(s) + Cl2(g) → 2 Na+Cl–(s)

Na is oxidized, Cl is reduced

Na is the reducing agent, Cl2 is the oxidizing agent

Identify the Oxidizing and Reducing Agents

in Each of the Following

3 H2S + 2 NO3– + 2 H+ 3 S + 2 NO + 4 H2O

MnO2 + 4 HBr  MnBr2 + Br2 + 2 H2O

Identify the Oxidizing and Reducing Agents

in Each of the Following

3 H2S + 2 NO3– + 2 H+ 3 S + 2 NO + 4 H2O

MnO2 + 4 HBr  MnBr2 + Br2 + 2 H2O

+1 -2 +5 -2 +1 0 +2 -2 +1 -2

ox ag

red ag

+4 -2 +1 -1 +2 -1 0 +1 -2

oxidation

reduction

oxidation

reduction

red ag

ox ag