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प्रश्न
Describe the oxidising action of potassium dichromate and write the ionic equation for its reaction with H2S.
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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)
H2S is oxidised to sulphur.
\[\ce{Cr2O^2-_7 + 8H^+ + 3H2S -> 2Cr^3+ + 7H2O + 3S}\]
संबंधित प्रश्न
The elements of 3d transition series are given as: Sc Ti V Cr Mn Fe Co
Answer the following: Which element shows only +3 oxidation state?
|
`E_((M^(2+)/M)` |
Cr | Mn | Fe | Co | Ni | Cu |
| -0.91 | -1.18 | -0.44 | -0.28 | -0.25 | -0.34 |
From the given data of E0 values, answer the following questions :
(1) Why is `E_(((Cu^(2+))/(Cu)))` value exceptionally positive
(2) Why is `E_(((Mn^(2+))/(Mn)))` value is highly negative as compared to other elements
(3) Which is the stronger reducing agents Cr2+ or Fe2+ ? Give Reason.
Which of the d-block elements may not be regarded as the transition elements?
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:
The d1 configuration is very unstable in ions.
The paramagnetic character in the 3d-transition series elements increases up to Mn and then decreases.
Maximum magnetic moment is shown by ____________.
In lake test for Al3+ ions, there is the formation of coloured ‘floating lake’. It is due to ______.
When \[\ce{KMnO4}\] solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time because ______.
Highest oxidation state of manganese in fluoride is \[\ce{+4 (MnF4)}\] but highest oxidation state in oxides is \[\ce{+7 (Mn2O7)}\] because ______.
Transition elements form binary compounds with halogens. Which of the following elements will form \[\ce{MF3}\] type compounds?
(i) \[\ce{Cr}\]
(ii) \[\ce{Co}\]
(iii) \[\ce{Cu}\]
(iv) \[\ce{Ni}\]
Match the properties given in Column I with the metals given in Column II.
| Column I (Property) | Column II (Metal) | |
| (i) | An element which can show +8 oxidation state | (a) \[\ce{Mn}\] |
| (ii) | 3d block element that can show | (b) \[\ce{Cr}\] |
| upto +7 oxidation state | (c) \[\ce{Os}\] | |
| (iii) | 3d block element with highest melting point | (d) \[\ce{Fe}\] |
Assertion: \[\ce{Cu^2+}\] iodide is not known.
Reason: \[\ce{Cu^2+}\] oxidises \[\ce{I^-}\] to iodine.
Identify the metal and justify your answer.
\[\ce{MO3F}\]
Mention the type of compounds formed when small atoms like H, C and N get trapped inside the crystal lattice of transition metals. Also give physical and chemical characteristics of these compounds.
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?
Which of the following characteristics of transition metals is associated with their catalytic activity?
Assertion (A): Transition metals have high enthalpy of atomisation.
Reason (R): Greater number of unpaired electrons in transition metals results in weak metallic bonding.
Which property of transition metals enables them to behave as catalysts?
What is the oxidation state of chromium in chromate ion and dichromate ion?
