The standard enthalpy change for reaction 3 is 354 kJ/mol and for reaction 4 is -3192 kJ/mol.
To calculate the standard enthalpy change of reaction for reactions 3 and 4, we can use average bond enthalpy values. For reaction 3, which is N₂(g) + 3H₂(g) → 2NH₃(g), we can use the average bond enthalpy values provided: N-H = 391 kJ/mol, H-H = 436 kJ/mol, N≡N = 945 kJ/mol.
To calculate the standard enthalpy change, we need to account for the bonds broken in the reactants and the bonds formed in the products. In this case, 1 N≡N bond (broken) and 6 N-H bonds (formed) are involved. Therefore, the standard enthalpy change for reaction 3 would be: (1 x 945) - (6 x 391) = 354 kJ/mol.
For reaction 4, which is C₇H₁₆(g) + 11O₂(g) → 7CO₂(g) + 8H₂O(g), we can use the average bond enthalpy values provided: O-H = 463 kJ/mol, C=O = 805 kJ/mol, O=O = 496 kJ/mol, C-H = 412 kJ/mol, C-C = 348 kJ/mol. To calculate the standard enthalpy change, we need to account for the bonds broken in the reactants and the bonds formed in the products.
In this case, 8 O-H bonds, 7 C=O bonds, 22 O=O bonds, 16 C-H bonds, and 14 C-C bonds are involved. Therefore, the standard enthalpy change for reaction 4 would be: (8 x 463) + (7 x 805) - (22 x 496) - (16 x 412) - (14 x 348) = -3192 kJ/mol.