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Thermodynamics

JEE Main 2024 (Online) 30th January Morning ShiftNumericalMedium📈 Topic in 29% papers+4
Ques. 1JEE Main 2024, 30 January (Morning Shift)

[figure] An ideal gas undergoes a cyclic transformation starting from the point A and coming back to the same point by tracing the path A B C A as shown in the diagram above. The total work done in the process is J.

Answer

200

Solution

Work on the gas: w = - P dV (1 kPa dm³ = 1 J)

A → B: P = 10 kPa, V 10 → 30 dm³ ⇒ w = −10 × 20 = −200 J

B → C: V 30 → 10 dm³, P 10 → 30 kPa ⇒ w = −(average P)ΔV = −20 × (−20) = +400 J

C → A: ΔV = 0 ⇒ w = 0

∴ Total w = −200 + 400 + 0 = +200 J (= area of triangle ABC = ½ × 20 × 20)

Answer: 200

Keep practising — Thermodynamics

Ques. 2JEE Main 2024, 30 January (Evening Shift)

Two reactions are given below: 2Fe(s) + 32O2(g) Fe2O3(s), H = -822 kJ/mol C(s) + 12O2(g) CO(g), H = -110 kJ/mol Then enthalpy change for following reaction 3C(s) + Fe2O3(s) 2Fe(s) + 3CO(g) is kJ/mol.

Ques. 3JEE Main 2024, 29 January (Morning Shift)

Which of the following is not correct?

  1. G is positive for a spontaneous reaction
  2. G is positive for a non-spontaneous reaction
  3. G is zero for a reversible reaction
  4. G is negative for a spontaneous reaction
Ques. 4JEE Main 2024, 29 January (Evening Shift)

Standard enthalpy of vapourisation for CCl4 is 30.5 kJ mol-1. Heat required for vapourisation of 284 g of CCl4 at constant temperature is kJ. (Given molar mass in g mol-1; C = 12, Cl = 35.5)

Ques. 5JEE Main 2024, 27 January (Morning Shift)

If three moles of an ideal gas at 300 K expand isothermally from 30 dm3 to 45 dm3 against a constant opposing pressure of 80 kPa, then the amount of heat transferred is J.

Ques. 6JEE Main 2024, 27 January (Evening Shift)

For a certain thermochemical reaction M N at T = 400 K, = 77.2 kJ mol-1, = 122 J K-1, log equilibrium constant (log K) is − 10-1.

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