Chemistry Class-11: Chapter –6. Thermodynamics Part – 7

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Question: 45

What will be the work done on an ideal gas enclosed in a cylinder, when it is compressed by a constant external pressure, in a single step as shown in Fig. 6.2. Explain graphically.

ideal gas enclosed in a cylinder

PV in Cylinder

ideal gas enclosed in a cylinder

Answer:

Work done on an ideal gas can be calculated from graph shown in Fig. 6.6. Work done is equal to the shaded area .

ideal gas enclosed in a cylinder

PV Curve Area

ideal gas enclosed in a cylinder

Question: 46

How will you calculate work done on an ideal gas in a compression, when change in pressure is carried out in infinite steps?

Answer:

The work done can be calculated with the help of plot of the work of compression which is carried out by change in pressure in infinite steps, is given in Fig. 6.7. Shaded area represents the work done on the gas.

Shaded area represents the work done on the gas.

PV Curve

Shaded area represents the work done on the gas.

Question: 47

Represent the potential energy/enthalpy change in the following processes graphically.

(a) Throwing a stone from the ground to roof.

(b)

In which of the processes potential energy/enthalpy change is contributing factor to the spontaneity?

Answer:

processes potential energy/enthalpy change is contributing factor

Distance vs. Energy

processes potential energy/enthalpy change is contributing factor

Fig.: 6.8 Enthalpy change in processes (a) and (b)

Question: 48

Enthalpy diagram for a particular reaction is given in Fig. 6.3. Is it possible to decide spontaneity of a reaction from given diagram. Explain.

Answer:

No.

Enthalpy is one of the contributory factors in deciding spontaneity but it is not the only factor. One must look for contribution of another factor i.e., entropy also, for getting the correct result.

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