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Thermodynamics

JEE Main 2025 (Online) 23rd January Evening ShiftMCQMedium📈 Topic in 29% papers+4−1
Ques. 1JEE Main 2025, 23 January (Evening Shift)

The effect of temperature on spontaneity of reactions are represented as : [figure] The incorrect combinations are :

  1. A and C only
  2. B and D only
  3. A and D only
  4. B and C only

Answer

(4) B and C only

Solution

G= H-T S<0 for spontaneity

A (+,-): G>0 at all T — correct

B (+,+): spontaneous only at high T (table says low T) — incorrect

C (-,-): spontaneous at low T (table says non-spontaneous) — incorrect

D (-,+): G<0 at all T — correct

∴ B and C are incorrect

Answer: (4)

Keep practising — Thermodynamics

Ques. 2JEE Main 2025, 23 January (Evening Shift)

The bond dissociation enthalpy of X2 H bond calculated from the given data is kJ mol-1. (Nearest integer) M+X-(s) M+(g)+X-(g) H lattice=800 kJ mol-1 M(s) M(g) H sub=100 kJ mol-1 M(g) M+(g)+e-(g) H i=500 kJ mol-1 X(g)+e-(g) X-(g) H eg=-300 kJ mol-1 M(s)+ 12X2(g) M+X-(s) H f=-400 kJ mol-1 [Given : M+X- is a pure ionic compound and X forms a diatomic molecule X2 in gaseous state]

Ques. 3JEE Main 2025, 22 January (Morning Shift)

A liquid when kept inside a thermally insulated closed vessel at 25 was mechanically stirred from outside. What will be the correct option for the following thermodynamic parameters ?

  1. U = 0, q < 0, w > 0
  2. U > 0, q = 0, w > 0
  3. U = 0, q = 0, w = 0
  4. U < 0, q = 0, w > 0
Ques. 4JEE Main 2025, 22 January (Evening Shift)

Match List - I with List - II. Choose the correct answer from the options given below :

  1. A-I, B-II, C-IV, D-III
  2. A-II, B-III, C-I, D-IV
  3. A-II, B-I, C-IV, D-III
  4. A-II, B-I, C-III, D-IV
Ques. 5JEE Main 2025, 22 January (Evening Shift)

Consider the following cases of standard enthalpy of reaction ( Hr in kJ mol-1) C2H6(g)+ 72O2(g) 2CO2(g)+3H2O(l) H1 =-1550 C(graphite)+O2(g) CO2(g) H2 =-393.5 H2(g)+ 12O2(g) H2O(l) H3 =-286 The magnitude of H f C2H6(g) is kJ mol-1 (Nearest integer).

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