Describe the preparation of potassium permanganate. How does the acidified permanganate solution react with oxalic acid ?
Write the ionic equations for the reactions.
Write the ionic equations for the reactions.
Potassium permanganate is prepared by fusion of MnO₂ with an alkali metal hydroxide and an oxidising agent like KNO₃. This produces the dark green K₂MnO₄ which disproportionates in a neutral or acidic solution to give permanganate.
2MnO₂ + 4KOH + O₂ → 2K₂MnO₄ + 2H₂O
3MnO₄²⁻ + 4H⁺ → 2MnO₄ + MnO₂ + 2H₂O
Oxalate ion or oxalic acid is oxidised at 333 K :
5C₂O₄²⁻ + 2MnO₄⁻ + 16H⁺ → 2Mn²⁺ + 8H₂O + 10CO₂
2MnO₂ + 4KOH + O₂ → 2K₂MnO₄ + 2H₂O
3MnO₄²⁻ + 4H⁺ → 2MnO₄ + MnO₂ + 2H₂O
Oxalate ion or oxalic acid is oxidised at 333 K :
5C₂O₄²⁻ + 2MnO₄⁻ + 16H⁺ → 2Mn²⁺ + 8H₂O + 10CO₂
Describe the oxidising action of potassium dichromate and write the ionic equations for its reaction with (i) an iodide (ii) H₂S.
Explain the following observation :
Most of the transition metal ions exhibit characteristic colour in aqueous solution.
Write the formula of an oxo-anion of Manganese (Mn) in which it shows the oxidation state equal to its group number.
What is meant by ‘disproportionation’ ? Give an example of a disproportionation reaction in aqueous solution.
Write the formula of an oxo-anion of Chromium (Cr) in which it shows the oxidation state equal to its group number.
Assign the reason for the following :
Copper (I) ion is not known in aqueous solution.
When Cu²⁺ ion is treated with KI, a white precipitate is formed. Explain the reaction with the help of chemical equation.
In a galvanic cell, the following cell reactions occurs:
E°cell = +1.56 V
(i) Is the direction of flow of electrons from zinc to silver or silver to zinc?
(ii) How will concentration of Zn²⁺ ions and Ag⁺ ions be affected when the cell functions?
Define the following terms :
(i) Molar conductivity (),
(ii) Secondary batteries.
Following reactions can occur at cathode during the electrolysis of aqueous silver nitrate solution using Pt electrodes:
What are the transition elements ? Write two characteristics of the transition elements.
Define azeotropes. What type of azeotrope is formed by positive deviation from Raoult’s law ?
Give an example.
Define the following terms :
(i) Fuel cell
(ii) Limiting molar conductivity