AIIMS 2011
- Exam
- AIIMS
- Year
- 2011
- Subject
- Chemistry
- Chapter
- Thermodynamics (C)
AIIMS 2011 · Chemistry · Thermodynamics (C)
The enthalpy of formation of CO_ (g) , CO_ 2(g), N_2 O_ (g) and N_2...
The enthalpy of formation of and is and respectively. For the reaction, is
Options
- A-212
- B+212
- C+48
- D-48
Correct answer
D. -48
Step-by-step solution
\begin{aligned}& \mathrm{N}_{2} \mathrm{O}_{4(g)}+3 \mathrm{CO}_{(g)} \longrightarrow \mathrm{N}}_{2} \mathrm{O}_{(g)}+3 \mathrm{CO}_{2(\mathrm{ g})}\\
& \Delta H_{\text{\text{ reaction } }}=\Sigma_{\text{Heat of formation of products }} \\
&-\Sigma_{\text{Heat of formation of reactants }}
\end{aligned}
\begin{aligned}& \Delta H_{\text{\text{ reaction } }}=\left[\Delta H_f \mathrm{ N}_{2} \mathrm{O}+3 \times \Delta H_f \mathrm{CO}}_{2}\right]- \\
& \quad\left[\Delta H_f \mathrm{ N}_{2} \mathrm{O}}_{4}+3 \times \Delta H_f \mathrm{CO}\right]\\
& \begin{aligned} \Delta H_r & =[+811+3(-393)]-[10+3(-110)] \\
& =[811-1179]-[-320]=-368+320 \\
& =-48 \mathrm{ kJ}/ \mathrm{mol}
\end{aligned}
\end{aligned}$