Chemistry Class 11 NCERT Solutions: Chapter 6 Thermodynamics Part 2

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Q: 7. In a process, of heat is absorbed by a system and work is done by the System. What is the change in internal energy for the process?

Answer:

According to the first law of thermodynamics,

Where,

Change in internal energy for a process

Given,

(Since heat is absorbed)

(Since work is done by the system)

Substituting the values in expression (i), we get

Hence, the change in internal energy for the given process is

Q: 8. The reaction of cyanamide, with dioxygen was carried out a bomb calorimeter, and ∆U was found to be Calculate enthalpy change for the reaction at

Answer:

Enthalpy change for a reaction (∆H) is given by the expression,

Where,

change in number of moles

For the given reaction,

And,

Substituting the values in the expression of ∆H:

Q: 9. Calculate the number of kJ of heat necessary to raise the temperature of of aluminium from Molar heat capacity of Al is

Answer

From the expression of heat (q),

Where,

Substituting the values in the expression of q:

Q: 10. Calculate the enthalpy change on freezing of of water at to ice at -

Answer:

Total enthalpy change involved in the transformation is the sum of the following changes:

(A) Energy change involved in the transformation of mol of water at

(B) Energy change involved in the transformation of

(C) Energy change involved in the transformation of

Hence, the enthalpy change involved in the transformation is