Question:
What is the stoichiometric coefficient of SO$_2$ in the following balanced reaction?
\[
{MnO}_4^-(aq) + {SO}_2(g) \rightarrow {Mn}^{2+}(aq) + {HSO}_4^-(aq)
\]
(in acidic solution)
What is the stoichiometric coefficient of SO$_2$ in the following balanced reaction?
\[
{MnO}_4^-(aq) + {SO}_2(g) \rightarrow {Mn}^{2+}(aq) + {HSO}_4^-(aq)
\]
(in acidic solution)
Show Hint
Balancing redox reactions involves writing the oxidation and reduction half reactions, balancing the electrons, and then combining the half reactions.
Updated On: Jan 13, 2026
- 5
- 4
- 3
- 2
Show Solution
Verified By Collegedunia
The Correct Option is A
Approach Solution - 1
Step 1: {Oxidation Half Reaction}
Write the oxidation half reaction: \[ {SO}_2(g) + 2 {H}_2{O}(l) \rightarrow {HSO}_4^-(aq) + 3 {H}^+(aq) + 2e^- \] Step 2: {Reduction Half Reaction}
Write the reduction half reaction: \[ {MnO}_4^-(aq) + 8 {H}^+(aq) + 5e^- \rightarrow {Mn}^{2+}(aq) + 4 {H}_2{O}(l) \] Step 3: {Balance the Electrons}
To balance the electrons, multiply the oxidation half reaction by 5 and the reduction half reaction by 2: \[ 5 {SO}_2(g) + 10 {H}_2{O}(l) \rightarrow 5 {HSO}_4^-(aq) + 15 {H}^+(aq) + 10e^- \] \[ 2 {MnO}_4^-(aq) + 16 {H}^+(aq) + 10e^- \rightarrow 2 {Mn}^{2+}(aq) + 8 {H}_2{O}(l) \] Step 4: {Combine and Simplify}
Combine the two half reactions: \[ 2 {MnO}_4^-(aq) + 5 {SO}_2(g) + 16 {H}^+(aq) \rightarrow 2 {Mn}^{2+}(aq) + 5 {HSO}_4^-(aq) + 8 {H}_2{O}(l) \] Thus, the stoichiometric coefficient of SO$_2$ is 5.
Write the oxidation half reaction: \[ {SO}_2(g) + 2 {H}_2{O}(l) \rightarrow {HSO}_4^-(aq) + 3 {H}^+(aq) + 2e^- \] Step 2: {Reduction Half Reaction}
Write the reduction half reaction: \[ {MnO}_4^-(aq) + 8 {H}^+(aq) + 5e^- \rightarrow {Mn}^{2+}(aq) + 4 {H}_2{O}(l) \] Step 3: {Balance the Electrons}
To balance the electrons, multiply the oxidation half reaction by 5 and the reduction half reaction by 2: \[ 5 {SO}_2(g) + 10 {H}_2{O}(l) \rightarrow 5 {HSO}_4^-(aq) + 15 {H}^+(aq) + 10e^- \] \[ 2 {MnO}_4^-(aq) + 16 {H}^+(aq) + 10e^- \rightarrow 2 {Mn}^{2+}(aq) + 8 {H}_2{O}(l) \] Step 4: {Combine and Simplify}
Combine the two half reactions: \[ 2 {MnO}_4^-(aq) + 5 {SO}_2(g) + 16 {H}^+(aq) \rightarrow 2 {Mn}^{2+}(aq) + 5 {HSO}_4^-(aq) + 8 {H}_2{O}(l) \] Thus, the stoichiometric coefficient of SO$_2$ is 5.
Was this answer helpful?
0
0
Show Solution
Verified By Collegedunia
Approach Solution -2
Step 1: Identify the redox nature of the reaction
This is a redox reaction in an acidic medium involving:
- \( MnO_4^- \) being reduced to \( Mn^{2+} \)
- \( SO_2 \) being oxidized to \( HSO_4^- \)
Step 2: Assign oxidation states
- In \( MnO_4^- \), Mn is in +7 oxidation state
- In \( Mn^{2+} \), Mn is in +2 oxidation state
⇒ Mn gains 5 electrons (reduction)
- In \( SO_2 \), S is in +4 oxidation state
- In \( HSO_4^- \), S is in +6 oxidation state
⇒ S loses 2 electrons (oxidation)
Step 3: Balance the electron transfer
To balance the electrons, we use the LCM of 5 and 2 = 10
- 2 \( MnO_4^- \) will gain 10 electrons
- 5 \( SO_2 \) will lose 10 electrons
Step 4: Balanced redox reaction in acidic medium
The balanced reaction becomes:
\[ 2MnO_4^- + 5SO_2 + 2H_2O \rightarrow 2Mn^{2+} + 5HSO_4^- + 2H^+ \]
Step 5: Identify the stoichiometric coefficient of SO₂
From the balanced equation, the coefficient of SO₂ is 5
Final Answer: 5
This is a redox reaction in an acidic medium involving:
- \( MnO_4^- \) being reduced to \( Mn^{2+} \)
- \( SO_2 \) being oxidized to \( HSO_4^- \)
Step 2: Assign oxidation states
- In \( MnO_4^- \), Mn is in +7 oxidation state
- In \( Mn^{2+} \), Mn is in +2 oxidation state
⇒ Mn gains 5 electrons (reduction)
- In \( SO_2 \), S is in +4 oxidation state
- In \( HSO_4^- \), S is in +6 oxidation state
⇒ S loses 2 electrons (oxidation)
Step 3: Balance the electron transfer
To balance the electrons, we use the LCM of 5 and 2 = 10
- 2 \( MnO_4^- \) will gain 10 electrons
- 5 \( SO_2 \) will lose 10 electrons
Step 4: Balanced redox reaction in acidic medium
The balanced reaction becomes:
\[ 2MnO_4^- + 5SO_2 + 2H_2O \rightarrow 2Mn^{2+} + 5HSO_4^- + 2H^+ \]
Step 5: Identify the stoichiometric coefficient of SO₂
From the balanced equation, the coefficient of SO₂ is 5
Final Answer: 5
Was this answer helpful?
0
0
Top BITSAT Chemistry Questions
- Which of the following silver salts is insoluble in water ?
- Which of the following is deliquescent ?
- Among the following sets of quantum numbers. Which one is incorrect for $4d$ electron ?
- In the purification of impure nickel by Mond's process, metal is purified by:
- When $25\, g$ of a non-volatile solute is dissolved in $100\,g$ of water, the vapour pressure is lowered by $2.25 \times 10^{-1}\, mm$. If the vapour pressure of water at $20^{\circ} C$ is $17.5\, mm$, what is the molecular weight of the solute?
View More Questions
Top BITSAT thermal properties of matter Questions
- A 1 L closed flask contains a mixture of 4 g of methane and 4.4 g of carbon dioxide. The pressure inside the flask at 27\degree C is (Assume ideal behaviour of gases):
- In which mode of expression, the concentration of a solution remains independent of temperature?
- The degeneracy of hydrogen atom that has energy equal to \(-\frac{R_H}{9}\) is (where \( R_H \) = Rydberg constant)
- If the de-Broglie wavelength of a particle of mass (\( m \)) is 100 times its velocity, then its value in terms of its mass (\( m \)) and Planck constant (\( h \)) is:
- The energy of the second orbit of a hydrogen atom is \( -5.45 \times 10^{-19} \) J. What is the energy of the first orbit of \( Li^{2+} \) ion (in J)?
View More Questions
Top BITSAT Questions
- Two point charges $-q$ and $+ q$ are located at point's $(0, 0, - a)$ and, $(0, 0, a)$ respectively. The electric potential at a point $(0, 9, z)$, where $z > a$ is
- Which of the following must be known in order to determine the power output of an automobile?
- A large drop of oil (density $0.8 \,g / cm ^{3}$ and viscosity $\eta_{0}$ ) floats up through a column of another liquid (density $1.2\, g / cm ^{3}$ and viscosity $\eta_{L}$ ). Assuming that the two liquids do not mix, the velocity with which the oil drop rises will depend on :
- A body is projected vertically upwards at time $ t = 0$ and it is seen at a height $H$ at time $t_1$ and $t_2$ second during its flight. The maximum height attained is ($g$ is acceleration due to gravity)
- At what point of a projectile motion, acceleration and velocity are perpendicular to each other ?
View More Questions