F5 C1 Redox Equilibrium

A redox reaction is a chemical reaction where oxidation and reduction occur simultaneously.

​

​Some text here about the topic of discussion.

​Redox reaction

Multiple Choice

Another name for a "oxidation-reduction" reaction is

• chemical reaction

• neutralization reaction

• redox reaction

• nuclear reaction

1. Gain or loss oxygen

Oxidation reaction takes place when a reactant gains oxygen. Reduction reaction takes place when a reactant loses oxygen.

Oxygen (O) atom​ no.

Mg: 0 → 1 O

C : 2O →​ 0

​Oxidation [O]: Mg

Reduction [R]: CO₂

Oxidation agent: CO₂

Reduction agent: Mg​

Multiple Choice

Is calcium oxidized or reduced in the following reaction? 

2 CaO → 2 Ca + O₂

• oxidized

• Reduced

Multiple Choice

Which of the following represents oxidation?

• C → CH₄

• Fe³⁺ → Fe²⁺

• Cl₂ → 2Cl^-

• Zn → ZnO

Multiple Choice

In the reaction,

Fe₂O₃(s) + 3CO(g) → 2Fe(l) + 3CO₂(g)

• carbon monoxide is reduced

• carbon monoxide is an oxidizing agent

• Iron (III) oxide is oxidised

• iron (III) oxide is the oxidizing agent

Multiple Select

Chemical equation : Zn + CuO → ZnO + Cu

which statements are true?

• Copper ion undergoes oxidation

• Zinc metal undergoes oxidation

• Oxidation number of zinc increases from 0 to +2

• Copper ion in CuO acts as oxidizing agent

​2. Gain and Loss of Hydrogen

Oxidation reaction takes place when a reactant loses hydrogen. Reduction reaction takes place when a reactant gain hydrogen.

Hydrogen (H) atom​ no.:

H₂S : 2H → 0 H

Cl₂ : 0 H →​ 1 H

​Oxidation [O]: H₂S

Reduction [R]: Cl₂

Oxidation agent: Cl₂

Reduction agent: H₂S​

​3. Electron Transfer

Oxidation reaction takes place when a reactant loses electrons. Reduction reaction takes place when a reactant gain electrons.

Some text here about the topic of discussion

​Oxidation [O]: Mg

Reduction [R]: O₂

Oxidation agent: O₂

Reduction agent: Mg​

​Half equation:

Oxidation [O]:​ Mg → Mg²⁺ + 2e^-

​Reduction [R]: O₂ + 4e^- → 2O^2-

Multiple Choice

The species that gain electron is _____ and usually the ____ agent

• oxidized; oxidizing

• reduced; reducing

• reduced; oxidizing

• oxidized; reducing

Multiple Choice

The species that loses electron is _____ and usually _____ agent.

• oxidized; reducing

• reduced; oxidizing

• oxidized; oxidizing

• reduced; reducing

Multiple Choice

Half equation : Br₂ + 2e^- --> 2Br^-

Which statement is correct?

• Bromine undergoes oxidation

• Bromine undergoes reduction

Multiple Choice

Which statement is true:

Mg → Mg²⁺ + 2e^–

• Mg gains 2 electron

• Mg²⁺ loses 2 electron

• Mg loses 1 electron

• Mg loses 2 electrons

Multiple Choice

Substance that oxidizes another substance by accepting its electrons.

• reducing agent

• oxidation agent

• oxidation number

Multiple Choice

Which one of the following conversions is an example of reduction?

• Copper (II) oxide to copper (II) sulfate

• Copper (II) oxide to copper

• Hydrochloric acid to chlorine

• Lead (II) nitrate to lead (II) chloride

Multiple Select

Which one of the following conversions is an example of reduction?

• removes hydrogen

• gains oxygen

• is reduced at the end of the reaction

• accepts electron

​4. Change in oxidation number

Oxidation reaction takes place when the oxidation number of an element increases.

Reduction reaction takes place when the oxidation number of an element decreases.

Oxidation​ no.:

C : 0 → +4

O : 0 →​ -2

​Oxidation [O]: C

Reduction [R]: O₂

Oxidation agent: O₂

Reduction agent: C​

OXIDATION NUMBER

oxidation number or oxidation state:

​​charge of the elements in a compound if the transfer of electrons occurs in an atom to form chemical bonds with other atoms.

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​​1. Element and monoatomic ion

i. Oxidation no. of each element is zero

ii. ​Oxidation no. of monoatomic ion is equal to the charge of ion.

​Element	​Oxidation no.	​Monoatomic ion	​Oxidation no.
​Sodium (Na)	​0	​Sodium ion (Na+)	​+1
​Oxygen gas (O	​0	​Oxide ion (O2-)	​-2
​Magnesium (Mg)	0​	​Magnesium ion (Mg2+)	+2​
​Aluminium (Al)	​0	​Aluminium ion (Al3+)	​+3
​Chlorine gas (Cl	​0	​Chloride ion (Cl-)	​-1

2. Sum of oxidation no.

i. Sum of oxidation no. of each element in the compound is zero

ii. ​Sum of oxidation no. of each element in polyatomic ion is equal to the charge of ion.

​​Example (compound):

NaCl = +1 + (-1) = 0

MgCl₂ = +2 + 2(-1) = 0

Al₂O₃ = 2(+3) + 3(-2) = 0​

​Example (polyatomic ion):

NH₄⁺ = (-3) + 4(+1) = +1

SO₄^2- = +6 + 4(-2) = -2

CO₃^2- = +4 + 3(-2) = -2

3. Oxidation no. for H, O & Group 17

• Elements in a transition group has more than 1 oxidation number.

​Element	​Normal Oxidation No.	​EXCEPT
​H	​+1	​in metal hydrides
O​	​-2	​in hydrogen peroxide
G17 (Cl, Br, I)​	​-1	​bound to more electronegative element (e.g. O)

​Example

Determine the oxidation number for the underlined elements. Show all workings, if any

1) Ba(OH)₂

x + 2(-2 + 1) = 0

x -4 = 0

x = +4​

​2) MnO₄^-

x + 4(-2) = -1​

x = -1 + 8

x = +7​

​​3) H₂O₂

2(+1) + 2x = 0

2 + 2x = 0

x = +1​

​​4) NaH

+1 + x = 0

x = -1

Multiple Choice

Oxidation number of N in NO₂ is

• +4

• +3

• +2

• +1

Multiple Choice

Oxidation number P in PO₄^3-

• +4

• +5

• +6

• +7

Multiple Choice

oxidation number Fe in FeCl₃ is

• +1

• +2

• +3

• +4

Multiple Choice

oxidation number Mg is

• -2

• 0

• +1

• +2

Multiple Choice

oxidation number Cu²⁺ is

• -1

• 0

• +1

• +2

Multiple Choice

Which equation represents a redox reaction?

• NaOH + HNO₃ → NaNO₃ + H₂O

• 2 AgNO₃ + Zn → Zn(NO₃)₂ + 2 Ag

• 2 NaCl + Pb(NO₃)₂ → PbCl₂ + 2 NaNO₃

• CaCO₃ + 2 HCl → CaCl₂ + H₂O + CO₂