back to directory
NEET PHYSICSThermodynamicsMedium

Question

One mole of an ideal diatomic gas undergoes a transition from AA to BB along a path ABAB as shown in the figure. The change in internal energy of the gas during the transition is

A

20 kJ20\text{ kJ}

B

20 kJ-20\text{ kJ}

C

20 J20\text{ J}

D

12 kJ-12\text{ kJ}

Step-by-Step Solution

For an ideal diatomic gas, the molar specific heat at constant volume is Cv=52RC_v = \frac{5}{2}R. The change in internal energy is a state function and depends only on the initial and final temperatures. It can be expressed as: ΔU=nCvΔT=n(52R)(TBTA)=52(nRTBnRTA)\Delta U = nC_v\Delta T = n\left(\frac{5}{2}R\right)(T_B - T_A) = \frac{5}{2}(nR T_B - nR T_A) Using the ideal gas equation PV=nRTPV = nRT, this becomes: ΔU=52(PBVBPAVA)\Delta U = \frac{5}{2}(P_B V_B - P_A V_A) From the standard PP-VV indicator diagram given in this PYQ, the coordinates for the initial state AA and final state BB are A(4 m3,5 kPa)A \equiv (4\text{ m}^3, 5\text{ kPa}) and B(6 m3,2 kPa)B \equiv (6\text{ m}^3, 2\text{ kPa}). Therefore, PAVA=5 kPa×4 m3=20 kJP_A V_A = 5\text{ kPa} \times 4\text{ m}^3 = 20\text{ kJ} and PBVB=2 kPa×6 m3=12 kJP_B V_B = 2\text{ kPa} \times 6\text{ m}^3 = 12\text{ kJ}. Substituting these values into the internal energy equation: ΔU=52(12 kJ20 kJ)=52(8 kJ)=20 kJ\Delta U = \frac{5}{2}(12\text{ kJ} - 20\text{ kJ}) = \frac{5}{2}(-8\text{ kJ}) = -20\text{ kJ}.

Exam Context & Concepts Covered

This question aligns with the NEET PHYSICS syllabus, specifically targeting concepts from Thermodynamics. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

PHYSICSThermodynamicsdiatomicundergoestransitionfigurechange

More Thermodynamics Questions

View all

The volume ($V$) of a monatomic gas varies with its temperature ($T$), as shown in the graph. The ratio of work done by the gas to the heat absorbed by it when it undergoes a change from state $A$ to state $B$ will be:

A.$\frac{2}{5}$
B.$\frac{2}{3}$
C.$\frac{1}{3}$
D.$\frac{2}{7}$
MediumSolve

A carnot engine having an efficiency of $\frac{1}{10}$ as a heat engine, is used as a refrigerator. If the work done on the system is $10\text{ J}$, the amount of energy absorbed from the reservoir at lower temperature is:

A.$1\text{ J}$
B.$90\text{ J}$
C.$99\text{ J}$
D.$100\text{ J}$
MediumSolve

An engine has an efficiency of $\frac{1}{6}$. When the temperature of the sink is reduced by $62^{\circ}\text{C}$, its efficiency is doubled. The temperature of the source is:

A.$124^{\circ}\text{C}$
B.$37^{\circ}\text{C}$
C.$62^{\circ}\text{C}$
D.$99^{\circ}\text{C}$
MediumSolve

A refrigerator works between $4^{\circ}\text{C}$ and $30^{\circ}\text{C}$. It is required to remove $600 \text{ calories}$ of heat every second to keep the temperature of the refrigerated space constant. The power required will be: (Take, $1 \text{ cal} = 4.2 \text{ Joules}$)

A.23.65 W
B.236.5 W
C.2365 W
D.2.365 W
MediumSolve

When $1 \text{ kg}$ of ice at $0^{\circ}\text{C}$ melts into water at $0^{\circ}\text{C}$, the resulting change in its entropy, taking the latent heat of ice to be $80 \text{ cal/g}$, is:

A.$8 \times 10^4 \text{ cal/K}$
B.$80 \text{ cal/K}$
C.$293 \text{ cal/K}$
D.$273 \text{ cal/K}$
EasySolve

The coefficient of performance of a refrigerator is $5$. If the temperature inside freezer is $-20^\circ\text{C}$, the temperature of the surroundings to which it rejects heat is

A.$31^\circ\text{C}$
B.$41^\circ\text{C}$
C.$11^\circ\text{C}$
D.$21^\circ\text{C}$
MediumSolve

A mass of diatomic gas ($\gamma=1.4$) at a pressure of $2\text{ atm}$ is compressed adiabatically so that its temperature rises from $27^\circ\text{C}$ to $927^\circ\text{C}$. The pressure of the gas in the final state is:

A.$28\text{ atm}$
B.$68.7\text{ atm}$
C.$256\text{ atm}$
D.$8\text{ atm}$
MediumSolve

An ideal gas is compressed to half its initial volume using several processes. Which of the processes results in the maximum work done on the gas?

A.adiabatic
B.isobaric
C.isochoric
D.isothermal
MediumSolve

This neet physics practice question is part of the TopperSquare free question bank. TopperSquare offers 15,000+ chapter-wise NEET MCQs across Physics, Chemistry, and Biology with detailed step-by-step explanations, full mock tests, NEET PYQs (2010–2024), and an AI-powered performance analytics dashboard. browse all neet practice questions → · practice physics sets →