Redox Reactions CBSE Questions & Answers

Redox Reactions

This is Chemistry Class 11 Redox Reactions CBSE Questions & Answers. There are 15 questions in this test with each question having around four answer choices.

Questions & Answers

The term oxidation was coined for the class of chemical reactions wherein one of the following options take place.

A
addition of oxygen to a substance
Correct
B
addition of electropositive element to a substance
C
removal of electronegative element from a substance
D
addition of hydrogen to a substance

The term reduction has one of the following options taking place.

A
removal of electropositive element from a substance
B
removal of oxygen from a substance
Correct
C
addition of electronegative element to a substance
D
removal of hydrogen to a substance

Oxidation and reduction always occur simultaneously, hence, the word “redox” was coined for this class of chemical reactions. In the following redox reaction, identify the species undergoing oxidation and reduction: \({\text{3F}}{{\text{e}}_{\text{3}}}{{\text{O}}_{\text{4}}}\left( {\text{s}} \right){\text{ }} + {\text{ 8 Al }}\left( {\text{s}} \right){\text{ }} \to {\text{ 9 Fe }}\left( {\text{s}} \right){\text{ }} + {\text{ 4A}}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{3}}}\left( {\text{s}} \right)\)

A
\({\text{F}}{{\text{e}}_{\text{3}}}{{\text{O}}_{\text{4}}}\) is oxidised, Fe is reduced
B
Aluminium is oxidised, \(({\text{F}}{{\text{e}}_{\text{3}}}{{\text{O}}_{\text{4}}})\) is reduced
Correct
C
\({\text{A}}{{\text{l}}_{\text{2}}}{{\text{O}}_{\text{3}}}\) is reduced, \({\text{F}}{{\text{e}}_{\text{3}}}{{\text{O}}_{\text{4}}}\) is oxidised
D
\({\text{F}}{{\text{e}}_{\text{3}}}{{\text{O}}_{\text{4}}}\) is oxidised, Aluminium is reduced

The formation of sodium chloride involves two half reaction, which clearly show involvement of electrons. 2 \({\text{Na}}\left( {\text{s}} \right){\text{ }} \to {\text{ 2 Na}} + \left( {\text{g}} \right){\text{ }} + {\text{ 2e}}\) \({\text{C}}{{\text{l}}_{\text{2}}}\left( {\text{g}} \right){\text{ }} + {\text{ 2e}}{\text{ }} \to {\text{ 2 Cl}}\left( {\text{g}} \right)\) Sum of the half reactions gives \({\text{2 Na}}\left( {\text{s}} \right){\text{ }} + {\text{C}}{{\text{l}}_{\text{2}}}\left( {\text{g}} \right){\text{ }} \to {\text{ 2 Na}} + {\text{ Cl}}{\text{ }}\left( {\text{s}} \right){\text{ or 2 NaCl }}\left( {\text{s}} \right)\) In terms of electron-transfer change, name the oxidising agent(s) and reducing agent(s)

A
oxidising agents:Chlorine, oxygen and sulphur and reducing agent:sodium
Correct
B
reducing agents:Chlorine, oxygen and sulphur and oxidising agent:sodium
C
oxidising agents:Chlorine, oxygen and reducing agents:sodium and sulphur
D
reducing agents:Chlorine, oxygen and oxidising agents:sodium and sulphur

Copper nitrate is a blue colour solution. Place a strip of metallic zinc in an aqueous solution of copper nitrate for about one hour. What happens?

A
zinc strip becomes coated with reddish metallic colour
Correct
B
the blue colour of the solution becomes more intense blue.
C
zinc strip becomes coated with blue colour
D
the blue colour of the solution turns to red

Redox reaction between copper and aqueous solution of silver nitrate happens when copper rod is dipped in silver nitrate solution. What happens in the final stage?

A
silver deposits in the solution; Ag+(aq) is reduced to Ag(s).
B
silver deposits on the rod; Ag+(aq) is oxidised to Ag(s)
C
copper deposits in the solution; Cu(aq) is reduced to \({\text{Cu}}_2^ + \) (s)
D
the solution turns intense blue due to the formation of \({\text{Cu}}_2^ + \) ions
Correct

The electron releasing tendency of the metals, zinc, copper and silver is in the order:

A
Zn>Cu>Ag
Correct
B
Cu>Ag>Zn
C
Zn>Ag>Cu
D
Ag>Cu>Zn

In the reaction of metallic cobalt placed in nickel sulphate solution, therein is a competition for release of electrons At equilibrium, chemical tests reveal that both \({\text{Ni}}_2^ + \) (aq) and \({\text{Co}}_2^ + \) (aq) are present at moderate concentrations. The result is that:

A
Only [Co(s) and \({\text{Ni}}_2^ + \) (aq)] are favoured
B
neither the reactants nor the products [are greatly favoured.
Correct
C
Only one reactant and one product is greatly favoured.
D
Only \({\text{Co}}_2^ + \) (aq) and Ni (s)] are favoured

Oxidation number denotes the oxidation state of an element in a compound ascertained on the basis that electron in a covalent bond belongs

A
entirely to more electronegative element
Correct
B
entirely to more electronegative element
C
entirely to halogens in a compound
D
entirely to transition elements if present

The highest value of oxidation number changes from 1 to 7

A
the first three groups
B
across the third period in the periodic table
Correct
C
In alkaline earth metals
D
in the atoms of transition elements

The oxidation number of oxygen in most compounds is

A
-2.0
Correct
B
-3
C
1
D
4

Aurous chloride and auric chloride are written as Au(l)Cl and Au(lll)Cl3.The roman numeral in parenthesis after the symbol of the metal in the molecular formula represents the

A
electronegativity
B
basic character
C
oxidation number
Correct
D
Ionic state

Formation of coloured solution is possible when metal ion in the compound contains

A
lone pair of electrons
B
negative ionic state
C
paired electrons
D
unpaired electrons
Correct

All combustion reactions, which make use of elemental dioxygen, as well as other reactions involving elements other than dioxygen are:

A
decomposition reactions
B
combination reactions
Correct
C
disproportionation reactions
D
displacement reactions

Standard electrode potential of three metals X, Y and Z are –1.2 V, +0.5 V and –3.0 V respectively. The reducing power of these metals will be

A
Y > Z > X
B
X > Y > Z
C
Y > X > Z
D
Z > X > Y
Correct