Advertisements
Advertisements
प्रश्न
How is potassium dichromate prepared from chrome iron ore?
Advertisements
उत्तर
Potassium dichromate is prepared from chromite ore (FeCr2O4) in the following steps.
Step (1): Preparation of sodium chromate
4FeCr2O4 + 16NaOH + 7O2 → 8NaCrO4 + 2Fe2O3 + 8H2O
Step (2): Conversion of sodium chromate into sodium dichromate
2Na2CrO4 + conc.H2SO4 → Na2Cr2O7 + Na2SO4 + H2O
Step(3): Conversion of sodium dichromate to potassium dichromate
Na2Cr2O7 + 2KCl → K2Cr2O7 + 2NaCl
Potassium dichromate being less soluble than sodium chloride is obtained in the form of orange coloured crystals and can be removed by filtration.
APPEARS IN
संबंधित प्रश्न
Explain why is Fe3+ more stable than Fe2+?
|
`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.
Account for the following:
E° value for the Mn3+/Mn2+ couple is much more positive than that for Cr3+/Cr2+.
Which of the 3d series of the transition metals exhibits the largest number of oxidation states and why?
Explain why Cu+ ion is not stable in aqueous solutions?
Describe the oxidising action of potassium dichromate and write the ionic equation for its reaction with iodide.
How would you account for the following:
The d1 configuration is very unstable in ions.
How would you account for the following?
Transition metals and their compounds act as catalysts.
Write balanced chemical equations for the conversion of `CrO_4^(2-)` to `Cr_2O_7^(2-)` in acidic medium and `Cr_2O_7^(2-)` to `CrO_4^(2-)`
in basic medium.
Complete and balance the following chemical equations
`MnO_4^(-) + H_2O + I^(-) ->`
Why does the density of transition elements increase from Titanium to Copper? (at. no. Ti = 22, Cu = 29)
Two metallic elements A and B have the following standard oxidation potentials: A = 0·40v B = - 0·80v. What would you expect if element A was added to an aqueous salt solution of element B? Give a reason for your answer.
Which is the most stable oxidation state of iron?
In lake test for Al3+ ions, there is the formation of coloured ‘floating lake’. It is due to ______.
Electronic configuration of a transition element X in +3 oxidation state is [Ar]3d5. What is its atomic number?
The halides of transition elements become more covalent with increasing oxidation state of the metal. Why?
Assertion: \[\ce{Cu^2+}\] iodide is not known.
Reason: \[\ce{Cu^2+}\] oxidises \[\ce{I^-}\] to iodine.
The element with atomic number 53 belongs to
Sodium this sulphate is used in photography because of its:-
On adding NaOH, solution to the aqueous solution of K2CrO7 the colour of the solution changes from
A complex in which dsp2 hybridisation takes place is ______.
Why is the `"E"_(("V"^(3+)//"V"^(2+)))^"o"` value for vanadium comparatively low?
How is the variability in oxidation states of transition metals different from that of p-block elements?
In the ground state of atomic Fe (Z = 26), the spin-only magnetic moment is ______ × 10-1 BM.
(Round off to the nearest integer).
[Given: `sqrt3 = 1.73, sqrt2 = 1.41`]
Which of the following ions has the electronic configuration 3d6?
(Atomic number: Mn = 25, Co = 27, Ni = 28)
A transition element X has an electronic configuration [Ar]4s23d3. Predict its likely oxidation states.
The compounds of \[\ce{Ti^4+}\] ions are colourless due to ______.
The E° value for the Mn2+/Mn2+ couple is more positive than that of Cr3+/Cr2+ or Fe3+/Fe2+ due to the change of:
