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enthalpy change...please help

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please help....1.Consider the reaction:Ch4(g)+Cl2(g) ? CH3Cl(g) +HCl(g)a.what bonds are broken and what bonds are formed?b.Calculate:i. the energy required to break these bondsii. the energy released on forming the bonds E(C---H)=415kJmol-1; E(Cl---Cl) = 242 kJmol-1; E(C---Cl) = 338 kJmol-1; ... 顯示更多 please help.... 1.Consider the reaction: Ch4(g)+Cl2(g) ? CH3Cl(g) +HCl(g) a. what bonds are broken and what bonds are formed? b. Calculate: i. the energy required to break these bonds ii. the energy released on forming the bonds E(C---H)=415kJmol-1; E(Cl---Cl) = 242 kJmol-1; E(C---Cl) = 338 kJmol-1; E(H---Cl)=431kJmol-1 更新: c. Hence calculate △H for the reaction d. Explain why the following reaction would have a similar value of △H: C2H6(g) +Cl2(g) ? C2H5Cl(g) + HCl(g) e. Explain why the experimental values for △H for the chlorination of methane and ethane are not identical in practice. 更新 2: 20 marks will be given to the best solution!!

最佳解答:

1a. CH3-H + Cl-Cl → CH3-Cl + H-Cl Bonds broken : a C-H bond, and a Cl-Cl bond Bonds formed : a C-Cl bond, and an H-Cl bond 1.b.i. Energy needed for bond breaking = 415 + 242 = 657 kJ mol-1 1.b.ii. Energy released in bond formation = 338 + 431 = 769 kJ mol-1 1.c. ΔH = 657 - 769 = -112 kJ mol-1 1.d. CH3-H + Cl-Cl → CH3-Cl + H-Cl CH3CH2-H + Cl-Cl → CH3CH2-Cl + H-Cl In either reaction, a C-H bond and a Cl-Cl are broken, while a C-Cl bond and an H-Cl bond are formed. 1.e. The exact bond enthalpy of a particular chemical bond depends on the molecular environment in which the bond exists. Therefore, the bond enthalpy of C-H bond in CH4 is not exactly the same as that in CH3CH3, and the bond enthalpy of C-Cl bond in CH3Cl is also not exactly the same as that in CH3CH2Cl.

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