25-10-2025
UNIT-IV
Question Bank
• Calculate Oxidation number of highlighted atom,
i. Cr₂O₇²⁻
ii. Fe³⁺
In the dichromate ion ( 2− ), the sum of the oxidation numbers of all the atoms must equal the charge
2 7
of the ion, which is -2.
Rule used: Oxygen usually has an oxidation number of -2, except in peroxides or when bonded to
fluorine.
1.Assign the known oxidation number of oxygen: -2.
2.Let be the unknown oxidation number of chromium (Cr).
3.Set up the equation based on the formula and the overall charge:
•2 (oxidation number of Cr) + 7 (oxidation number of O) = Overall charge 2( )+7(−2)=−2
4.Solve for
2 −14=−2−2+14
2 =12
The oxidation number of chromium (Cr) in 2 2−7 is +6.
=+6
, 25-10-2025
• Calculate Oxidation number of highlighted atom,
i. Cr₂O₇²⁻
ii. Fe³⁺
Fe³⁺ (ferric ion)
For a monatomic (single-atom) ion, the oxidation number is equal to its charge.
Rule used: The oxidation number of a monatomic ion is equal to the charge of
the ion.
•The charge of the ferric ion is +3.
The oxidation number of iron (Fe) in 3+ is +3.
Redox Titration
Balance the given redox reaction, derive factor and
discuss type of titration with procedure.
(Atomic weight K = 39, Br = 79 amu)
a. IO₃⁻ → I₂
I⁻ → I₂
This reaction is a comproportionation where iodine in the +5 and -1 oxidation states
reacts to form iodine in the 0 oxidation state. It is performed in an acidic medium.
Comproportionation a type of redox reaction where two
reactants containing the same element in different
oxidation states form a single product in which the
element is in an intermediate oxidation state.
, 25-10-2025
Redox Titration
Balance the given redox reaction, derive factor and
discuss type of titration with procedure.
(Atomic weight K = 39, Br = 79 amu)
a. IO₃⁻ → I₂
I⁻ → I₂
This reaction is a comproportionation where iodine in the +5 and -1 oxidation states
reacts to form iodine in the 0 oxidation state. It is performed in an acidic medium.
Redox Titration
Balance the given redox reaction, derive factor and
discuss type of titration with procedure.
(Atomic weight K = 39, Br = 79 amu)
a. IO₃⁻ → I₂
I⁻ → I₂
This reaction is a comproportionation where iodine in the +5 and -1 oxidation states
reacts to form iodine in the 0 oxidation state.
It is performed in an acidic medium.
This reaction is the basis for iodometric titration.
This is an indirect titration method used to determine the concentration of an
oxidizing agent (in this case, − ). An excess of iodide ( −) is added to the oxidizing
3
agent, which liberates a stoichiometric amount of iodine ( 2). The amount of
liberated 2is then determined by titrating it with a standard reducing agent, like
sodium thiosulfate.
UNIT-IV
Question Bank
• Calculate Oxidation number of highlighted atom,
i. Cr₂O₇²⁻
ii. Fe³⁺
In the dichromate ion ( 2− ), the sum of the oxidation numbers of all the atoms must equal the charge
2 7
of the ion, which is -2.
Rule used: Oxygen usually has an oxidation number of -2, except in peroxides or when bonded to
fluorine.
1.Assign the known oxidation number of oxygen: -2.
2.Let be the unknown oxidation number of chromium (Cr).
3.Set up the equation based on the formula and the overall charge:
•2 (oxidation number of Cr) + 7 (oxidation number of O) = Overall charge 2( )+7(−2)=−2
4.Solve for
2 −14=−2−2+14
2 =12
The oxidation number of chromium (Cr) in 2 2−7 is +6.
=+6
, 25-10-2025
• Calculate Oxidation number of highlighted atom,
i. Cr₂O₇²⁻
ii. Fe³⁺
Fe³⁺ (ferric ion)
For a monatomic (single-atom) ion, the oxidation number is equal to its charge.
Rule used: The oxidation number of a monatomic ion is equal to the charge of
the ion.
•The charge of the ferric ion is +3.
The oxidation number of iron (Fe) in 3+ is +3.
Redox Titration
Balance the given redox reaction, derive factor and
discuss type of titration with procedure.
(Atomic weight K = 39, Br = 79 amu)
a. IO₃⁻ → I₂
I⁻ → I₂
This reaction is a comproportionation where iodine in the +5 and -1 oxidation states
reacts to form iodine in the 0 oxidation state. It is performed in an acidic medium.
Comproportionation a type of redox reaction where two
reactants containing the same element in different
oxidation states form a single product in which the
element is in an intermediate oxidation state.
, 25-10-2025
Redox Titration
Balance the given redox reaction, derive factor and
discuss type of titration with procedure.
(Atomic weight K = 39, Br = 79 amu)
a. IO₃⁻ → I₂
I⁻ → I₂
This reaction is a comproportionation where iodine in the +5 and -1 oxidation states
reacts to form iodine in the 0 oxidation state. It is performed in an acidic medium.
Redox Titration
Balance the given redox reaction, derive factor and
discuss type of titration with procedure.
(Atomic weight K = 39, Br = 79 amu)
a. IO₃⁻ → I₂
I⁻ → I₂
This reaction is a comproportionation where iodine in the +5 and -1 oxidation states
reacts to form iodine in the 0 oxidation state.
It is performed in an acidic medium.
This reaction is the basis for iodometric titration.
This is an indirect titration method used to determine the concentration of an
oxidizing agent (in this case, − ). An excess of iodide ( −) is added to the oxidizing
3
agent, which liberates a stoichiometric amount of iodine ( 2). The amount of
liberated 2is then determined by titrating it with a standard reducing agent, like
sodium thiosulfate.
