Identify the type of reaction:
(i) CH4(g) + 2O2(g) → CO2(g)+ 2H2O(g)
(ii) 2NaCI(l) 
2Na(s) + Cl2(g)
(iii) MnO2 + 4HCI 
MnCl2 + 2H2O+ Cl2
(i) CH4(g) + 2O2 (g) → CO2 (g) + 2H2O (g): This is an example of Exothermic reaction because it leads to release of HEAT as can be seen water is given in gaseous form.
(ii) 2NaCI(l) 
2Na (s) + Cl2 (g) : This is the example of Decomposition reaction of common salt using electricity. This reaction is also called Electrolysis of Bryn solution.
(iii) MnO2 + 4HCI → MnCl2 + 2H2O+ Cl2
This reaction is the example of a redox reaction. Because MnO2 has donated its oxygen atoms and hence got reduced. Also, Chlorine is converted into Cl- to form Cl2 and hence get oxidised. Since both oxidation and reduction has taken place. This is a redox reaction.