273018 If the mass defect of 5B11 is 0.081u, its average binding energy (in MeV ) is :
Given: Δm=0.081u.Number of nucleons =11∴ Binding energy =Δm×931MeV=0.081×931=75.411MeVand average binding energy= Binding energy Number of nucleons =75.41111=6.85MeV.
273019 Given, the bond energies of N≡N,H−H and N−H bonds as 945,436 and 391 kJ/mol respectively, the enthalpy of the reaction
Given, the reaction isN2+3H2⟶2NH3Bond energy of N≡N=945 kJ/mole.Bond energy of 3(H−H)=3×436=1308 kJ/moleBond energy of 6( N−H)=6×391=2346 kJ/mole∴ Enthalpy of reaction = reactant - product=945+1308−2346=2253−2346=−93kJmol−1
273020 Average C−H bond energy is 416 kJ mol−1. Which of the following is correct?
CH4 consists of C−H bonds.To break CH4 into C and 4H, the energy required =4×416=1664 kJ∴ The requirement satisfied by the following.CH4( g)+1664 kJ→C(g)+4H(g)
273022 Find the ΔH0 for the reaction H2O(g) +Br2( g)→HBr(g)+HOBr(g) using:Bond energy of O−H bond in Water =463 kJBond energy of Br−Br bond in Br2=192 kJBond energy of O−Br bond in HOBr=234 kJBond energy of H−Br bond in HBr=364 kJ
The heat of reaction can be calculated based on the standard heat of formation of all reactants involved.ΔH∘=[(234+364)−(463+192)]=598−655=−57 kJ mol−1