Question

both please

Carbon tetrachloride can be promed by reacting chlorine with methane : ICHq + 2Cl2 -> CCl4 t 2 H₂ Given that the heat of formation of methane is - 24.85k] Imol and the heat of porination of carbon tetrachloride is - 135k3 /mol, determine the standard enthaalpy of formation poi the reaction Why are there not values For the heat og og pormation of Cl2 and H₂ ? Is this ieaction endothermic or lexothermic ? How do you know?

Answer 1

of methane is, AHF (che) AHO 2 The given reaction is: CHy+ ach cal4 + 24 Now, in the gaseous state the formation heat :- 74.85 KJ/mol. And, heat of formation of celyis, Ahof (4) 3 - 135kJ/mol. Head of formations of Hy sch are 'O'. The stand and enthalpy of the reaction is: A Hof(product) - Ahof (recefant) >[135-(-74.85] kJ/mol 2 (135 +74.85) KJ/mol =-60.15 kg/mol Heat of Enthalpy of the reaction is: ~60-15kg/mol. The formation reactions of cl and thy are: 2cl cl 821 h Thus, we see that during the formation of the and Ch, there is no nef change, this eventually we don't expect any energy chage here. This is why Cl2 8th has to formation The heat of reaction is! AH²2-60.15 kJ/mol, the sign is negative (-ve), that means heat is liberated to the system, thus, the reaction is exothermic. Here, we are calculating the heat of reaction by just playing with the formation heats. But in principle we could have done the same using the bond energies is by calculating the differences of energy when the 4c-ce bonds form and 46-H bonds break. Ines, it is a direct method of calculation of enthalpy of reaction. This is why the calculation with formation heat is considered as indirect method. heat. 3