Advertisements
Advertisements
Question
Balance the following reaction by oxidation number method.
\[\ce{MnO^-_{4(aq)} + Br^-_{ (aq)}->MnO2_{ (s)} + BrO^-_{3(aq)}(basic)}\]
Advertisements
Solution
\[\ce{MnO^-_{4(aq)} + Br^-_{ (aq)}->MnO2_{ (s)} + BrO^-_{3(aq)}(basic)}\]
Step 1: Write a skeletal equation and balance the elements other than O and H.
\[\ce{MnO^-_{4(aq)} + Br^-_{ (aq)}->MnO2_{ (s)} + BrO^-_{3(aq)}}\]
Step 2: Assign the oxidation number to Mn and Br. Calculate the increase and decrease in the oxidation number and make them equal.
Increase in oxidation number:
(Increase per atom = 6)
Decrease in oxidation number:
(Decrease per atom = 3)
To make the net increase and decrease equal, we must take 2 atoms of Mn.
\[\ce{2MnO^-_{4(aq)} + Br^-_{ (aq)}->2MnO2_{ (s)} + BrO^-_{3(aq)}}\]
Step 3: Balance 'O' atoms by adding H2O to the right-hand side.
\[\ce{2MnO^-_{4(aq)} + Br^-_{ (aq)}->2MnO2_{ (s)} + BrO^-_{3(aq)} + H2O_{(l)}}\]
Step 4: The medium is basic. To make the charges and hydrogen atoms on the two sides equal, add 2H+ on the left-hand side.
\[\ce{2MnO^-_{4(aq)} + Br^-_{ (aq)} + 2H^+_{ (aq)}->2MnO2_{ (s)} + BrO^-_{3(aq)} + H2O_{(l)}}\]
Add OH− ions equal to the number of H+ ions on both sides of the equation.
\[\ce{2MnO^-_{4(aq)} + Br^-_{ (aq)} + 2H^+_{ (aq)} + 2OH^-_{( aq)}->2MnO2_{ (s)} + BrO^-_{3(aq)} + H2O_{(l)} + 2OH^-_{( aq)}}\]
The H+ and OH− ions appearing on the same side of the reaction are combined to give H2O molecules.
\[\ce{2MnO^-_{4(aq)} + Br^-_{ (aq)} + 2H2O_{(l)}->2MnO2_{ (s)} + BrO^-_{3(aq)} + H2O_{(l)} + 2OH^-_{( aq)}}\]
\[\ce{2MnO^-_{4(aq)} + Br^-_{ (aq)} + H2O_{(l)}->2MnO2_{ (s)} + BrO^-_{3(aq)} + 2OH^-_{( aq)}}\]
Step 5: Check two sides for balance of atoms and charges.
Hence, balanced equation: \[\ce{2MnO^-_{4(aq)} + Br^-_{ (aq)} + H2O_{(l)}->2MnO2_{ (s)} + BrO^-_{3(aq)} + 2OH^-_{( aq)}}\]
APPEARS IN
RELATED QUESTIONS
Calculate the oxidation number of sulphur, chromium and nitrogen in H2SO5, `"Cr"_2"O"_7^(2-)` and `"NO"_3^-`. Suggest structure of these compounds. Count for the fallacy.
Whenever a reaction between an oxidising agent and a reducing agent is carried out, a compound of lower oxidation state is formed if the reducing agent is in excess and a compound of higher oxidation state is formed if the oxidising agent is in excess. Justify this statement giving three illustrations.
How do you count for the following observations?
Though alkaline potassium permanganate and acidic potassium permanganate both are used as oxidants, yet in the manufacture of benzoic acid from toluene we use alcoholic potassium permanganate as an oxidant. Why? Write a balanced redox equation for the reaction.
Balance the following equation in basic medium by ion-electron method and oxidation number methods and identify the oxidising agent and the reducing agent.
\[\ce{P4(s) + OH–(aq) —> PH3(g) + HPO^–_2(aq)}\]
Balance the following equation in the basic medium by ion-electron method and oxidation number methods and identify the oxidising agent and the reducing agent.
\[\ce{N2H4(l) + ClO^-_3 (aq) → NO(g) + Cl–(g)}\]
Balance the following equation in basic medium by ion-electron method and oxidation number methods and identify the oxidising agent and the reducing agent.
\[\ce{Cl_2O_{7(g)} + H_2O_{2(aq)} -> ClO-_{2(aq)} + O_{2(g)} + H+_{(aq)}}\]
Chlorine is used to purify drinking water. Excess of chlorine is harmful. The excess of chlorine is removed by treating with sulphur dioxide. Present a balanced equation for this redox change taking place in water.
Justify that the following reaction is redox reaction; identify the species oxidized/reduced, which acts as an oxidant and which acts as a reductant.
\[\ce{2Cu2O_{(S)} + Cu2S_{(S)}->6Cu_{(S)} + SO2_{(g)}}\]
Balance the following reaction by oxidation number method.
\[\ce{Cr2O^2-_{7(aq)} + SO^2-_{3(aq)}->Cr^3+_{ (aq)} + SO^2-_{4(aq)}(acidic)}\]
Balance the following redox equation by half-reaction method.
\[\ce{H2C2O_{4(aq)} + MnO^-_{4(aq)}->CO2_{(g)} + Mn^2+_{( aq)}(acidic)}\]
Balance the following redox equation by half-reaction method.
\[\ce{Bi(OH)_{3(s)} + SnO^2-_{2(aq)}->SnO^2-_{3(aq)} + Bi^_{(s)}(basic)}\]
Which of the following is INCORRECT for the following reaction?
\[\ce{2Zn_{(s)} + O2_{(g)} -> 2ZnO_{(s)}}\]
Which of the following is a redox reaction?
Consider the reaction:
\[\ce{6 CO2(g) + 6H2O(l) → C6 H12O6(aq) + 6O2(g)}\]
Why it is more appropriate to write these reaction as:
\[\ce{6CO2(g) + 12H2O(l) → C6 H12O6(aq) + 6H2O(l) + 6O2(g)}\]
Also, suggest a technique to investigate the path of the redox reactions.
Balance the following equations by the oxidation number method.
\[\ce{I2 + NO^{-}3 -> NO2 + IO^{-}3}\]
Balance the following equations by the oxidation number method.
\[\ce{MnO2 + C2O^{2-}4 -> Mn^{2+} + CO2}\]
Identify the redox reactions out of the following reactions and identify the oxidising and reducing agents in them.
\[\ce{3HCl (aq) + HNO3 (aq) -> Cl2 (g) + NOCl (g) + 2H2O (l)}\]
Identify the redox reactions out of the following reactions and identify the oxidising and reducing agents in them.
\[\ce{HgCl2 (aq) + 2KI (aq) -> HgI2 (s) + 2KCl (aq)}\]
Identify the redox reactions out of the following reactions and identify the oxidising and reducing agents in them.
\[\ce{Fe2O3 (s) + 3CO (g) ->[Δ] 2Fe (s) + 3CO2 (g)}\]
Identify the redox reactions out of the following reactions and identify the oxidising and reducing agents in them.
\[\ce{PCl3 (l) + 3H2O (l) -> 3HCl (aq) + H3PO3 (aq)}\]
Balance the following ionic equations.
\[\ce{Cr2O^{2-}7 + Fe^{2+} + H+ -> Cr^{3+} + Fe^{3+} + H2O}\]
In acidic medium, reaction, \[\ce{MNO^-_4 → Mn^2+}\] an example of ____________.
The weight of CO is required to form Re2(CO)10 will be ______ g, from 2.50 g of Re2O7 according to given reaction
\[\ce{Re2O7 + CO -> Re2(CO)10 + CO2}\]
Atomic weight of Re = 186.2; C = 12 and O = 16.
Consider the following reaction:
\[\ce{xMnO^-_4 + yC2O^{2-}_4 + zH^+ -> xMn^{2+} + 2{y}CO2 + z/2H2O}\]
The values of x, y, and z in the reaction are, respectively:
