Q6 of 216 Page 469

No chemical reaction takes place when granules of a solid, A are mixed with the powder of another solid, B. However when the mixture is heated, a reaction takes place between its components. One of the products, C is a metal and settles down in the molten state while the other product, D floats over it. It was observed that the reaction is highly exothermic.

i. Based on the given information make an assumption about A and B and write a chemical equation for the chemical reaction indicating the conditions of reaction, physical state of reactants and products and thermal status of reaction.


ii. Mention any two types of reactions under which above chemical reaction can be classified.

i. Solid A is assumed to be MnO2 and solid B to be Aluminium (Al). When the mixture of MnO2 and Al is heated, manganese (Mn) is produced in molten state and aluminium oxide (Al2O3) floats over it. Mn is produced in the molten state as a lot of heat energy is released in the process. Therefore, “C” is Mn and “D” is Al2O3.


Reaction involved:


3Mn O2(s) + 4Al(s)→ 3Mn(l) + 2Al2O3(s) + Heat


ii. The types of reaction under which the above reaction is classified are:


a. Redox reaction


Redox (reduction–oxidation reaction) is a chemical reaction in which the oxidation states of atoms are changed. Any such reaction involves both a reduction process and a complementary oxidation process, two key concepts involved with electron transfer processes.


Oxidation is the loss of electrons or an increase in oxidation state by a molecule, atom, or ion.


Reduction is the gain of electrons or a decrease in oxidation state by a molecule, atom, or ion.


b. Displacement reaction


A displacement reaction is a type of reaction where part of one reactant is replaced by another reactant. A displacement reaction is also known as a replacement reaction or a metathesis reaction.


An example is the reaction between iron and copper sulfate to produce iron sulfate and copper:


Fe + CuSO4 → FeSO4 + Cu


Here, both iron and copper have the same valence. One metal cation takes the place of the other bonding to the sulphate anion.


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