# Chemical Thermodynamics Chapter 4 Chemistry Class 12 Textbook Solution

### 3. Answer in brief.

vi. Obtain the expression for work done in chemical reaction.

- In chemical reactions, work is performed when the system is held at constant temperature and pressure. This can be described by the equation:
- If we assume that the external pressure (\(P_{\text{ext}}\)) is equal to the system pressure (\(P\)), we can simplify the equation as follows:
- When dealing with ideal gases at constant temperature and pressure, we can use the following relationships:
- Equation (4) represents the work done by the system during chemical reactions.

W = -P_{ext}ΔV ....(1)

W = -PΔV

= -P(V_{2} - V_{1})

W = -PV_{2} + PV_{1} .....(2)

PV_{1} = n_{1}RT

PV_{2} = n_{2}RT ....(3)

By substituting equation (3) into equation (2), we obtain:

W = -n_{2}RT + n_{1}RT

= -(n_{2} - n_{1})RT

= -Δn_{g}RT .....(4)

Chemical Thermodynamics Chapter 4 Chemistry Class 12 Textbook Solution