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.
Name the following :
(i) A transition metal which does not exhibit variation in oxidation state in its compounds.
(ii) A compound where the transition metal is in the +7 oxidation state.
(iii) A member of the lanthanoid series which is well known to exhibit +4 oxidation state.
(iv) Ore used in the preparation of Potassium dichromate.
Calculate the degree of dissociation (α) of acetic acid if its molar conductivity () is 39.05 Scm² mol⁻¹. Given (H⁺) = 349.6 Scm² mol⁻¹ and (CH₃COO⁻) = 40.9 Scm² mol⁻¹..
Define the following terms :
(i) Fuel cell
(ii) Limiting molar conductivity
What is meant by rate of a reaction ? Differentiate between average rate and instantaneous rate of a reaction.
Define the following terms :
(i) Mole fraction
(ii) Isotonic solutions
(iii) Van’t Hoff factor
(iv) Ideal solution
Define the following terms:
(i) Abnormal molar mass
(ii) van’t Hoff factor