Answer
See the explanation
Work Step by Step
To estimate the change in energy (ΔE) for the given reactions in the gas phase, we can use the bond energy values provided in Table 3-3.
a. $H_{2}+Cl_{2}\rightarrow 2HCl$
The bond energies involved in this reaction are:
- H-H bond energy: 436 kJ/mol
- Cl-Cl bond energy: 243 kJ/mol
- H-Cl bond energy: 431 kJ/mol
The change in energy (ΔE) can be calculated as follows:
ΔE = (2 × 431 kJ/mol) - (1 × 436 kJ/mol + 1 × 243 kJ/mol)
ΔE = 862 kJ/mol - 679 kJ/mol
ΔE = 183 kJ/mol
Therefore, the estimated change in energy (ΔE) for the reaction $H_{2}+Cl_{2}\rightarrow 2HCl$ in the gas phase is -183 kJ/mol, indicating that the reaction is exothermic.
b. $N\equiv N+3H_{2}\rightarrow 2NH_{3}$
The bond energies involved in this reaction are:
- N≡N bond energy: 945 kJ/mol
- H-H bond energy: 436 kJ/mol
- N-H bond energy: 391 kJ/mol
The change in energy (ΔE) can be calculated as follows:
ΔE = -(6 × 391 kJ/mol) = (1 × 945 kJ/mol + 3 × 436 kJ/mol)
ΔE = -93 kJ/mol
Therefore, the estimated change in energy (ΔE) for the reaction $N\equiv N+3H_{2}\rightarrow 2NH_{3}$ in the gas phase is -93 kJ/mol, indicating that the reaction is exothermic.
