[SAMMY]

HELP NEEDED>>>

Anyone can help me with this question ASAP.... please

(a)   Distinguish clearly between the terms mean bond energy  and bond dissociation energy.

Use the following reactions in your answer:

   H2O(g)  H(g) + OH(g)

   OH(g)   H(g) + O(g)                     (3 marks)

(b)   From the mean bond enthalpy data given below, estimate the enthalpy  change for the complete combustion of two moles of C2H6 (g) at 298 K.  (The molar enthalpy of vaporization of water is 45.0 kJ mol-1 at 298K).
   2C2H6 + 14 O2 --------------------- 4CO2 + 6H2O

Reactants - Products
Bond   CH   O=O   OH   C=O   CC
Bond enthalpy/kJ mol1   414   499   460   799   
347

(c)  A sample of naphthalene  C10H8 (s), is completely burned in a bomb calorimeter at 298K. The calorimeter constant (heat capacity) is 70.5 J K1. The standard molar enthalpy of combustion of naphthalene is  ΔcHo = – 5157 kJ mol1.
(i) Write a balanced chemical equation for the combustion reaction. 
C10H8 + 7O2          5CO2 + 4H2O
(ii) Calculate  DeltaUo for the reaction.                                                    
(iii) If the sample contains 200 mg naphthalene, calculate the heat released during the reaction, and hence calculate the temperature change of the calorimeter.        
(d)  Calculate the heat required to melt 500 kg of potassium metal at 336 K.
      The enthalpy of fusion of potassium is 2.35 kJ mol1.            

[Borek]

Please read forum rules.

[SAMMY]

For Part b)

Is it sum of Reactants - sum of products?? values from mean bond enthalpies!!!!

for working out Delta U is it the formula Delat H = Delta U - Delta (PV) where PV = nRT

Help im confused please..