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प्रश्न
Describe the oxidising action of potassium dichromate and write the ionic equation for its reaction with iron (II) solution.
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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.
\[\ce{Cr2O^2-_7 + 14H^+ + 6e- -> 2Cr^3+ + 7H2O}\]
\[\ce{6Fe^2+ -> 6Fe^3+ + 6e-}\]
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\[\ce{Cr2O^2-_7 + 14H^+ + 6Fe^2+ -> 2Cr^3+ + 7H2O + 6Fe^3+}\]
संबंधित प्रश्न
Complete the following chemical equations:
`(i) Cr_2O_7^(2-)+6Fe^(2+)+14H^+ ->`
`(ii) 2CrO_4^(2-)+2H^+ ->`
`(iii) 2MnO_4^-+5C_2O_4^(2-)+16H^+ ->`
Predict which of the following will be coloured in the aqueous solution?
Ti3+, V3+, Cu+, Sc3+, Mn2+, Fe3+ and Co2+. Give reasons for each.
How would you account for the following:
Of the d4 species, Cr2+ is strongly reducing while manganese (III) is strongly oxidising.
Write down the number of 3d electrons in the following ion:
Cu2+
Indicate how would you expect the five 3d orbitals to be occupied for this hydrated ion (octahedral).
Give reasons Iron has the higher enthalpy of atomization than that of copper.
Which among the following transition metal has the lowest melting point?
Maximum magnetic moment is shown by ____________.
\[\ce{KMnO4}\] acts as an oxidising agent in acidic medium. The number of moles of \[\ce{KMnO4}\] that will be needed to react with one mole of sulphide ions in acidic solution is ______.
Which of the following will not act as oxidising agents?
(i) \[\ce{CrO3}\]
(ii) \[\ce{MoO3}\]
(iii) \[\ce{WO3}\]
(iv) \[\ce{CrO^{2-}4}\]
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 |
When an oxide of manganese (A) is fused with KOH in the presence of an oxidising agent and dissolved in water, it gives a dark green solution of compound (B). Compound (B) disproportionates in neutral or acidic solution to give purple compound (C). An alkaline solution of compound (C) oxidises potassium iodide solution to a compound (D) and compound (A) is also formed. Identify compounds A to D and also explain the reactions involved.
Identify the metal and justify your answer.
Carbonyl \[\ce{M(CO)5}\]
It has been observed that first ionization energy of 5 d series of transition elements are higher than that of 3d and 4d series, explain why?
The element with atomic number 46 belongs to
Which of the following species has maximum magnetic momentum?
On adding NaOH, solution to the aqueous solution of K2CrO7 the colour of the solution changes from
Account for the following:
Ce4+ is a strong oxidising agent.
Write the number of unpaired electrons in Cr3+.
(Atomic number of Cr = 24)
Account for the following:
Copper has an exceptionally positive `"E"_("M"^(2+)//"M")^0` value.
Compare the general characteristics of the first series of the transition metals with those of the second and third series metals in the respective vertical columns. Give special emphasis on the following point:
Ionisation enthalpies
