Question 98: Thermodynamics & KTG

Question

Consider the following statements:
A. Zeroth law of thermodynamics gives concept of temperature
B. First law of thermodynamics gives concept of internal energy
C. In isothermal expansion of ideal gas, $\Delta Q 
eq \Delta W$
D. Product of intensive and extensive variables is extensive
E. The ratio of any extensive variable to mass will be an extensive variable
Choose the correct combination of statements from the options given below:

Accepted Answer

Let us check each statement one by one.
Statement A
Zeroth law of thermodynamics gives concept of temperature
This is
correct
.
The zeroth law says that if two systems are separately in thermal equilibrium with a third system, then they are in thermal equilibrium with each other. This gives the basis for the
concept of temperature
.
So,
A is true
.
Statement B
First law of thermodynamics gives concept of internal energy
This is also
correct
.
The first law is
$$ \Delta Q = \Delta U + \Delta W $$
or equivalently,
$$ \Delta U = \Delta Q - \Delta W $$
This law introduces the thermodynamic state function
internal energy
.
So,
B is true
.
Statement C
In isothermal expansion of ideal gas, $\Delta Q 
eq \Delta W$
This is
incorrect
.
For an ideal gas in an
isothermal process
, temperature remains constant, so change in internal energy is zero:
$$ \Delta U = 0 $$
From the first law,
$$ \Delta Q = \Delta U + \Delta W $$
Hence,
$$ \Delta Q = \Delta W $$
So the statement says $\Delta Q 
eq \Delta W$, which is wrong.
Thus,
C is false
.
Statement D
Product of intensive and extensive variables is extensive
This is
correct
.
Recall:
Intensive variable
: does not depend on amount of substance, like pressure, temperature.
Extensive variable
: depends on amount of substance, like volume, mass, internal energy.
If an intensive quantity is multiplied by an extensive quantity, the result is generally
extensive
.
Example:
$$ P 	imes V $$
Here, pressure $P$ is intensive and volume $V$ is extensive. Their product behaves as an
extensive
quantity.
So,
D is true
.
Statement E
The ratio of any extensive variable to mass will be an extensive variable
This is
incorrect
.
Mass is itself an
extensive
variable.
So,
$$ \frac{	ext{extensive variable}}{	ext{mass}} $$
gives a
specific property
, which is an
intensive
variable.
Example:
$$ 	ext{specific volume} = \frac{V}{m} $$
This is an
intensive
property.
So,
E is false
.
Final conclusion
True statements are:
$$ A,\ B,\ D $$
Therefore, the correct option is:
$$ \boxed{	ext{Option C: A, B and D Only}} $$

Answer

C, D and E Only

Answer

A, B and C Only

Answer

A, B and D Only

Answer

B, C and D Only

Thermodynamics & KTG

Choose the correct answer: