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Thermodynamics

JEE Main 2026 (Online) 6th April Morning ShiftMCQMedium📈 Topic in 29% papers+4−1
Ques. 1JEE Main 2026, 6 April (Morning Shift)

Arrange the following isothermal processes in order of the magnitude of the work (p − V) involved between states 1 and 2. Choose the correct option.

  1. |wB| > |wA| > |wC| > |wD|
  2. |wC| > |wD| > |wA| > |wB|
  3. |wC| > |wD| > |wB| > |wA|
  4. |wB| > |wA| > |wD| > |wC|

Answer

(3) |wC| > |wD| > |wB| > |wA|

Solution

For an isothermal change between the same two states, |w| = area under the p–V path.

Expansion (work done by the gas, against pext lower than the gas pressure):

Single stage — whole expansion against the final (lowest) pressure ⇒ smallest area ⇒ |wA| is the least

Multi stage — higher external pressure in the early steps ⇒ larger area ⇒ |wB| > |wA|

Compression (work done on the gas, by pext higher than the gas pressure):

Single stage — whole compression at the final (highest) pressure ⇒ largest area ⇒ |wC| is the greatest

Multi stage — lower external pressure in the early steps ⇒ smaller area ⇒ |wC| > |wD|

∵ every compression path lies above the reversible isotherm and every expansion path lies below it

⇒ |wD| > |wrev| > |wB|

∴ |wC| > |wD| > |wB| > |wA|

Answer: (3)

Keep practising — Thermodynamics

Ques. 2JEE Main 2026, 6 April (Morning Shift)

Consider the reaction X Y at 300 K. If H and K are 28.40 kJ mol-1 and 1.8 10-7 at the same temperature, then the magnitude of S for the reaction in J K-1 mol-1 is . (Nearest integer) (Given : R = 8.3 J K-1 mol-1, ln 10 = 2.3, log 3 = 0.48, log 2 = 0.30)

Ques. 3JEE Main 2026, 6 April (Evening Shift)

Match List - I with List - II. Given V1 and V2 are initial and final volumes respectively. Choose the correct answer from the options given below :

  1. A-II, B-III, C-I, D-IV
  2. A-II, B-I, C-IV, D-III
  3. A-II, B-I, C-III, D-IV
  4. A-I, B-II, C-III, D-IV
Ques. 4JEE Main 2026, 5 April (Evening Shift)

Consider the following data for the reaction X2(g) + Y2(g) 2XY(g) at 600 K. The rG (in kJ mol-1) for the reaction is : array|c|c|c| Compound & fH 600 K ( kJ mol-1) & S 600 K ( J mol-1 K-1) \ XY(g) & 42 & 200 \ X2(g) & 8 & 140 \ Y2(g) & 80 & 250 \ array

  1. −21000
  2. −10
  3. −1000
  4. −9.012
Ques. 5JEE Main 2026, 5 April (Evening Shift)

The correct order of molar heat capacities measured at 298 K and 1 bar is :

  1. Copper(s) > Bromine(l) > Helium(g)
  2. Bromine(l) > Copper(s) > Helium(g)
  3. Helium(g) > Bromine(l) > Copper(s)
  4. Helium(g) > Bromine(l) = Copper(s)
Ques. 6JEE Main 2026, 4 April (Morning Shift)

Given below are two statements : In the light of the above statements, choose the correct answer from the options given below

  1. Both Statement I and Statement II are true
  2. Both Statement I and Statement II are false
  3. Statement I is true but Statement II is false
  4. Statement I is false but Statement II is true
Ques. 7JEE Main 2026, 4 April (Evening Shift)

If 3.365 g of ethanol (l) is burnt completely in a bomb calorimeter at 298.15 K, the heat produced is 99.472 kJ. The | Hf | of ethanol at 298.15 K is 102 kJ mol-1. (Nearest integer) Given: Standard enthalpy for combustion of graphite = −393.5 kJ mol-1 Standard enthalpy of formation of water (l) = −285.8 kJ mol-1 Molar mass in g mol-1 of C, H, O are 12, 1 and 16 respectively

Ques. 8JEE Main 2026, 2 April (Morning Shift)

Consider the following data. (i) 2Al(s) + 6HCl(aq) Al2Cl6(aq) + 3H2(g) + 1200 kJ/mol (ii) H2(g) + Cl2(g) 2HCl(g) + 164 kJ/mol (iii) HCl(g) + aq HCl(aq) + 83 kJ/mol (iv) Al2Cl6(s) + aq Al2Cl6(aq) + 663 kJ/mol The enthalpy of formation of anhydrous solid Al2Cl6 is :

  1. -648 kJ mol-1
  2. -1350 kJ mol-1
  3. -2002 kJ mol-1
  4. -1527 kJ mol-1
Ques. 9JEE Main 2026, 2 April (Morning Shift)

At the transition temperature T, A B and G = 105 - 35 T where A and B are two states of substance X. The transition temperature in °C when pressure is 1 atm is . (Nearest integer)

Ques. 10JEE Main 2026, 2 April (Evening Shift)

Gas 'A' undergoes change from state 'X' to state 'Y'. In this process, the heat absorbed and work done by the gas is 10 J and 18 J respectively. Now gas is brought back to state 'X' by another process during which 6 J of heat is evolved. In the reverse process of 'Y' to 'X',

  1. 18 J of the work is done by the gas 'A'.
  2. 2 J of the work is done by the gas 'A'.
  3. 12 J of the work is done on the gas 'A' by the surrounding.
  4. 14 J of the work is done on the gas 'A' by the surrounding.
Ques. 11JEE Main 2026, 28 January (Morning Shift)

20.0 dm3 of an ideal gas 'X' at 600 K and 0.5 MPa undergoes isothermal reversible expansion until pressure of the gas is 0.2 MPa. Which of the following option is correct? (Given: 2 = 0.3010 and 5 = 0.6989)

  1. w = -9.1 kJ, U = 0, H = 0, q = 9.1 kJ
  2. w = 9.1 J, U = 9.1 J, H = 0; q = 0
  3. w = -3.9 kJ, U = 0, H = 0; q = 3.9 kJ
  4. w = +4.1 kJ, U = 0, H = 0; q = -4.1 kJ

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