redox reactions

Question 1

What is the classical definition of oxidation and reduction?

Answer 1

oxidation: gain of oxygen, reduction: loss of oxygen
oxidation: loss of hydrogen, reduction: gain of hydrogen

Question 2

What is the modern definition of oxidation and reduction?

Answer 2

Oxidation: loss of electrons, Reduction: gain of electrons
Oxidation: increase in oxidation no., Reduction: decrease in oxidation no.

Question 3

A redox reaction is made up of __ (number) _______: oxidation and reduction. A ______ shows the loss or gain of electrons during redox reactions

Answer 3

A redox reaction is made up of 2 half-reactions: oxidation and reduction. A half-equation shows the loss or gain of electrons during redox reactions

Question 4

What is an oxidation number?

Answer 4

The oxidation number of an element is the charge that an atom of an element would have if it exists as an ion in a compound

Question 5

For an atom in its elemental form, the oxidation number is always __
For any monoatomic ion, the oxidation number is _____________
The sum of the oxidation numbers in a polyatomic ion equals _________

Answer 5

For an atom in its elemental form, the oxidation number is always zero
For any monoatomic ion, the oxidation number is equal to the charge of the ion
The sum of the oxidation numbers in a polyatomic ion equals the charge of the ion

Question 6

The oxidation number of oxygen is usually __ in both ionic and molecular compounds except in peroxides that contain the O2 2- ion, giving each oxygen an oxidation number of __
The oxidation number of hydrogen is usually __ when bonded to non-metal and __ when bonded to metal ions.
The oxidation number of fluorine is __ in all compounds

Answer 6

The oxidation number of oxygen is usually -2 in both ionic and molecular compounds except in peroxides that contain the O2 2- ion, giving each oxygen an oxidation number of -1
The oxidation number of hydrogen is usually +1 when bonded to non-metal and -1 when bonded to metal ions.
The oxidation number of fluorine is -1 in all compounds

Question 7

E.g.: Fe2O3 (s) + 3CO (g) –> 2Fe (s) + 3CO2 (g)

Identify the substance that has been reduced during the reaction.

Answer 7

Fe2O3 (reactant) is reduced as the oxidation number of Fe decreases from +3 in Fe2O3 to 0 in Fe.

Question 8

E.g.: Fe2O3 (s) + 3CO (g) –> 2Fe (s) + 3CO2 (g)

Identify the substance that has been oxidised during the reaction.

Answer 8

CO (reactant) is oxidised as the oxidation number of C increases from +2 in CO to +4 in CO2.

Question 9

What is a disproportionation reaction?

Answer 9

A disproportionation reaction occurs when the same element in a substance is both oxidised and reduced simultaneously to form 2 different products.