Short Answer TypeDistinguish between paramagnetism and ferro-magnetism. How does ferro magnetism arise?
Long Answer Type(i) Breifly explain the physical properties of lanthanoids.
(ii) The chemical reactivity of lanthanoids resembles to which other elements of the periodic table.
Short Answer TypeHow does the acidified KMnO4 react with the following:
(a) Iron(II) solution, (b)SO32–, (c) Iodide (I–) ion, (d) oxalic acid, (e) NO2– (Nitrite ion).
Long Answer TypeExplain any one of following statement:
(i) The transition metals are well known for the formation of interstitial compounds.
(ii) The largest number of oxidation states are exhibited by mangnese in the first series of transition elements.
Short Answer TypeAnswer the following questions:
(i) Which element in the first series of transition elements does not exhibit variable oxidation states and why?
(ii) Why do actinoids in general exhibit a greater range of oxidation states than the Lanthanoids?
Long Answer Typei)Describe how potassium permanganate is made from pyrolusite. Write the chemical equations for the involved reactions.
ii) Describe with an example each of the oxidising actions of permanganate ion in alkaline and acidic media. What acid and alkali are usually used?
Describe how potassium dichromate is made from chromate ore and give the equations for the chemical reactions involved.
Write balanced ionic equations for reacting ions to represent the action of acidified potassium dichromate solution on:
(a) Potassium iodide solution.
(b) Acidified ferrous sulphate solution. Write two uses of potassium dichromate.
1)Potassium dichromate (K2Cr2O7) is prepared from chromite ore FeCr2O4. The chromite ore is fused with sodium or potassium carbonate in free access of air.
4FeCr2O4 + 8Na2CO3 + 7O2 -------> 8Na2CrO4 + 2FeO3 + 8CO2
The yellow solution of sodium chromate is filtered and acidified with sulfuric acid to give a solution from which orange sodium dichromate , Na2Cr2O7 .2H2O can be crystallized.
2Na2CrO4 + 2H+ ---------> Na2Cr2O7 + 2Na + H2O
Sodium dichromate is more soluble than potassium dichromate. Hence sodium dichromate when fused with KCl forms orange crystals of potassium dichromate.
Na2Cr2O7 + 2KCl --------> K2Cr2O7 + 2NaCl
a) Iodine is liberated from potassium iodide :
10I– + 2MnO4– + 16H+ ——> 2Mn2+ + 8H2O + 5I2
b) Fe2+ ion (green) is converted to Fe3+ (yellow):
5Fe2+ + MnO4– + 8H+ ——> Mn2+ + 4H2O + 5Fe3+
uses of potassium dichromate
an oxidant, potassium permanganate can act as an antiseptic.
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