In: Chemistry
Use average bond energies to estimate the enthalpy changes of the following reactions: a. N2(g) + 3 H2(g) -> 2 NH3(g) b. N2(g) + 2 H2(g) -> H2NNH2(g) c. 2 N2(g) + O2(g) -> 2 N2O(g)
Using Bond energy values to calculate enthalpy of rxn:
a) N2 (g) +3H2(g)---->2NH3(g)
Bonds breaking in reactants | bond energy in KJ |
NN | 1mol*941KJ/mol941KJ |
H-H | 3mol*(432KJ/mol)1296KJ |
bond making in products | bond energy in KJ |
N-H | 6mol*(391KJ/mol)2346KJ |
- | - |
enthalpy of rxnenergy required for bond breaking-energy required for bond making(941+1296)-2346-109 KJ
enthalpy change of rxn -109KJ
b) N2 (g) +2H2(g)---->H2NNH2(g)
Bonds breaking in reactants | bond energy in KJ |
NN | 1mol*941KJ/mol941KJ |
H-H | 2mol*(432KJ/mol)864KJ |
bond making in products | bond energy in KJ |
N-H | 4mol*(391KJ/mol)1564KJ |
N-N | 1mol*160KJ/mol160KJ |
enthalpy of rxnenergy required for bond breaking-energy required for bond making(941+864)-(1564+160)81 KJ
enthalpy changes of rxn81KJ
c)2N2 (g) +O2(g)---->2N2O(g)
N2O structure:NN-O
Bonds breaking in reactants | bond energy in KJ |
NN | 2mol*941KJ/mol1882KJ |
OO | 1mol*(495KJ/mol)495KJ |
bond making in products | bond energy in KJ |
NN | 2mol*941KJ/mol1882KJ |
N-O | 2mol*201KJ/mol402KJ |
enthalpy of rxnenergy required for bond breaking-energy required for bond making(1882+495)-(1882+402) 93KJ
enthalpy changes of rxn93KJ