Advertisements
Advertisements
प्रश्न
Describe the oxidising action of potassium dichromate and write the ionic equation for its reaction with iron (II) solution.
Advertisements
उत्तर
Potassium dichromate acts as a strong oxidising agent. It is used as a primary standard in volumetric analysis. The oxidation action of dichromate ion in an acidic medium can be represented as follows:
\[\ce{Cr2O^{2-}_7 + 14H^+ + 6e^- -> 2Cr^{3+} + 7H2O}\] (E– = 1.33 V)
When ferrous salts (Fe2+) are treated with acidified K2Cr2O7, they are oxidised to ferric (Fe3+) salts.
\[\ce{Cr2O^2-_7 + 14H^+ + 6e- -> 2Cr^3+ + 7H2O}\]
\[\ce{6Fe^2+ -> 6Fe^3+ + 6e-}\]
_________________________________________________
\[\ce{Cr2O^2-_7 + 14H^+ + 6Fe^2+ -> 2Cr^3+ + 7H2O + 6Fe^3+}\]
संबंधित प्रश्न
Account for the following:
Cu+2 salts are coloured, while Zn2+ salts are white.
Which is a stronger reducing agent, Cr2+ or Fe2+ and why?
Calculate the ‘spin only’ magnetic moment of \[\ce{M^{2+}_{( aq)}}\] ion (Z = 27).
What are the characteristics of the transition elements and why are they called transition elements?
In what way is the electronic configuration of the transition elements different from that of the non-transition elements?
How is potassium dichromate prepared from chrome iron ore?
Explain why Mn2+ is more stable than Fe2+ towards oxidation to +3 state. (At. no. of Mn = 25, Fe = 26)
Give reason for the following:
The transition metals generally form coloured compounds.
Ionisation enthalpies of Ce, Pr and Nd are higher than Th, Pa and U. Why?
A solution of \[\ce{KMnO4}\] on reduction yields either a colourless solution or a brown precipitate or a green solution depending on pH of the solution. What different stages of the reduction do these represent and how are they carried out?
Match the catalysts given in Column I with the processes given in Column II.
| Column I (Catalyst) | Column II (Process) |
| (i) \[\ce{Ni}\] in the presence of hydrogen | (a) Zieglar Natta catalyst |
| (ii) \[\ce{Cu2C12}\] | (b) Contact process |
| (iii) \[\ce{V2O5}\] | (c) Vegetable oil to ghee |
| (iv) Finely divided iron | (d) Sandmeyer reaction |
| (v) \[\ce{TiCl4 + Al (CH3)3}\] | (e) Haber's Process |
| (f) Decomposition of KCIO3 |
Assertion: \[\ce{Cu^2+}\] iodide is not known.
Reason: \[\ce{Cu^2+}\] oxidises \[\ce{I^-}\] to iodine.
Account for the following:
In case of transition elements, ions of the same charge in a given series show progressive decrease in radius with increasing atomic number.
Which of the following is non-metallic?
Photographic film and plates have - au essential ingredient of
The product of oxidation of I– with \[\ce{MnO^{-}4}\] in alkaline medium is:-
On adding NaOH, solution to the aqueous solution of K2CrO7 the colour of the solution changes from
Which of the following characteristics of transition metals is associated with their catalytic activity?
Assertion (A): Transition metals show their highest oxidation state with oxygen.
Reason (R): The ability of oxygen to form multiple bonds to metals.
Explain the use of different transition metals as catalysts.
