Chemical Thermodynamics Chapter 4 Chemistry Class 12 Textbook Solution
4. Answer the following questions.
xx. Calculate the work done and comment on whether work is done on or by the system for the decomposition of 2 moles of
NH4NO3 at 100 0C NH4NO3(s)→ N2O(g) + 2H2O(g)
Ans. (-18.61 kJ, work is done by the system)
answer:-
**Given:**
Decomposition of 1 mole of NH4NO3
Temperature = \(T = 100^\circ\)C = 373 K
**To find:**
Work done and to determine whether work is done on the system or by the system
**Formula:**
\[W = -\Delta n_g RT\]
**Calculation:**
The given reaction is for 1 mole of NH4NO3. For 2 moles of NH4NO3, the reaction is given as follows:
\[2\text{NH}_4\text{NO}_3(s) \rightarrow 2\text{N}_2\text{O(g)} + 4\text{H}_2\text{O(g)}\]
Now,
\[\Delta n_g = (\text{moles of product gases}) - (\text{moles of reactant gases})\]
\[\Delta n_g = 6 - 0 = +6 \text{ mol} \quad (\text{since NH}_4\text{NO}_3\text{ is in solid state})\]
Hence,
\[W = -\Delta n_gRT\]
\[= -(+6 \text{ mol}) \times 8.314 \text{ J K}^{-1} \text{ mol}^{-1} \times 373 \text{ K}\]
\[= -18606.75 \text{ J}\]
\[= -18.61 \text{ kJ}\]
Work is done by the system (since \(W < 0\)).
The work done is -18.61 kJ. The work is done by the system.
Chemical Thermodynamics Chapter 4 Chemistry Class 12 Textbook Solution