NEET WEEKLY TEST CHEMISTRY (20.09.2025)

1. For a reaction: ΔH = +50.0 kJ·mol⁻¹ and ΔS = +75 J·mol⁻¹·K⁻¹. Find the minimum temperature above which the reaction becomes spontaneous.

2. One mole of an ideal gas expands isothermally & reversibly at 300 K from 2 L to 20 L. (R = 2 cal·mol⁻¹·K⁻¹). What will be the change in free energy at this same temperature if ΔH = 5 kcal.mol⁻¹?

3. For a reaction: ΔH = +50.0 kJ·mol⁻¹ and ΔS = +90 J·mol⁻¹·K⁻¹. Find the minimum temperature above which the reaction becomes spontaneous.

1) 100 K
2) 273 K
3) 625 K
4) 500 K

4. Given standard enthalpies of formation (ΔHf°):
ΔHf°(CH₄, g) = −74.8 kJ·mol⁻¹
ΔHf°(CO₂, g) = −393.5 kJ·mol⁻¹
ΔHf°(H₂O, l) = −285.8 kJ·mol⁻¹
Calculate ΔH for the reaction :
CH₄(g) + 2 O₂(g) → CO₂(g) + 2 H₂O(l)

1) −965.1 kJ
2) −818.7 Kj
3) −890.3 kJ
4) −74.8 kJ

5. Two ideal gases, X and Y, are initially separated by a removable partition in a thermally insulated, rigid container at uniform temperature. The partition is removed and they mix irreversibly. Which statement is always true about the entropy and heat exchange of the system?

1. ΔS_total = 0 and heat is absorbed from surroundings.
2. ΔS_total > 0 and no heat is exchanged with surroundings.
3. ΔS_total < 0 and heat is released to surroundings.
4. ΔS_total = 0 and no heat is exchanged with surroundings.

6. Which of the following statements correctly distinguishes a reversible process from an irreversible one?

1. In a reversible process ΔS_universe > 0; in an irreversible one ΔS_universe = 0.
2. A reversible process is one that occurs quickly; an irreversible one is slow.
3. A reversible process proceeds through a continuous sequence of equilibrium states and ΔS_universe = 0.
4. Reversibility depends only on the magnitude of ΔH for the process.

7. Which of the following is always positive?

1. ΔH for freezing of water at 1 atm
2. ΔS for vaporization of a liquid at its boiling point
3. ΔG for a reaction at equilibrium
4. ΔH for neutralization of a weak acid with a strong base

8. For a reaction, if ΔG° = 0, what can be concluded about the equilibrium constant (K)?

1. K = 1
2. K > 1
3. K < 1
4. No relation between ΔG° and K

9. Why does Hess’s law hold true?

1. Because enthalpy depends on the path of the reaction.
2. Because enthalpy is a state function.
3. Because entropy is always conserved.
4. Because ΔG is always negative.

10. One mole of water at 373 K and 1 atm absorbs 40.7 kJ heat during vaporization. What is ΔS for the phase change?

1. 40.7 J·mol⁻¹·K⁻¹
2. 109 J·mol⁻¹·K⁻¹
3. 0 J·mol⁻¹·K⁻¹
4. 373 J·mol⁻¹·K⁻¹

11. For the reaction:
H₂(g) + Cl₂(g) → 2HCl(g),
ΔH = −184.6 kJ at 298 K. What is ΔU? (R = 8.314 J·mol⁻¹·K⁻¹)

1)−184.6 kJ
2) −182.1 kJ
3)−187.1 kJ
4) −190.0 kJ

12. For free expansion of an ideal gas in an isolated container:

1. ΔU = 0, q = 0, w = 0
2. ΔU ≠ 0, q = 0, w = 0
3. ΔU = 0, q ≠ 0, w = 0
4. ΔU ≠ 0, q ≠ 0, w ≠ 0

13. For a reaction, ΔG° = +10 kJ·mol⁻¹ at 298 K. Which of the following is correct?

1. Equilibrium constant K > 1
2. Equilibrium constant K < 1
3. Reaction will never proceed forward.
4. ΔH = 0.

14. Which of the following is correct?

1. All exothermic reactions are spontaneous.
2. All endothermic reactions are non-spontaneous.
3. Spontaneity depends on both ΔH and ΔS.
4. Spontaneity is independent of entropy.

15. In which case the change in entropy is negative?

1. Sublimation of a solid to gas
2. 2H(g) → H₂​ (g)
3. Evaporation of water
4. Expansion of a gas at constant temperature

16. Which of the following is a polar molecule?

1) SiF₄
2) XeF₄
3) BF₃
4) SF₄

17. The number of lone pairs on Xe in XeF₂,XeF₄ and XeF₆ respectively are

1) 3, 2, 1
2) 2, 4, 6
3) 1, 2, 3
4) 6, 4, 2

18. Which of the following molecules/ions does not contain unpaired electrons?

1) O₂^2-
2) B₂
3) N₂⁺
4) O₂

19. Which of the following has pπ-dπ bonding ?

1) CO₂
2)  SO₃^2-
3) .NO₃^–
4) BO₃^2-

20. Which of the following has maximum ionic character?

1) NaCl
2) KCl
3) CsCl
4) RbCl

21. Which one of the following molecules contains no π bond ?

1) CO₂
2) SO₂
3) HCN 
4) H₂O

22. During the change of O₂ to O₂^–, the incoming electron goes to the orbital :

1) σ*2p_z
2) π*2p_x
3) π*2p_y
4) π2p_x

23. Which of the following pairs of ions are isoelectronics and isostructural ?

1) ClO₃^–, CO₃^2-
2) PCl₅, POCl₃
3) ClO₃^–, SO₃^2–
4) SF₆,ClF₃

24. Total number of lone pair of electrons on XeOF₄ is ?

1) 1
2) 2
3) 3
4) 4

25. The following pair which contain polar molecule is

1. CCl₄ and CO₂
2. PF₅ and XeF₄
3. SiF₄ and SbCl₅
4. BeCl₂ and SF₄

26. Which Hybridisation is not match with the following compound?

1) SO₄^2-  – sp³
2) NH₄⁺ – sp³
3) BrF₅ – sp³d³
4) SF₆ – sp³d²

27. Which of the following has the highest lattice energy ?

1) LiF
2) RbF
3) KF
4) NaF

28. Two pi and half sigma bonds are present in

1) N₂⁺
2) N₂
3) O₂
4) O₂⁺

29. Which among the following are diamagnetic?

1) O₂
2) N₂
3) O₂⁺
4) CO⁺

30. Choose the incorrect about the d-orbitals used in different types of hybridizations

1. sp³d- d_x2-y2
2. sp³d² – d_x2-y2, d_z2
3. sp³d³ – d_xy, d_yz, d_zx
4. dsp² – d_x2-y2

31. In the following equilibrium reaction 2A ⇋B+C, the equilibrium concentrations of A, B and C are 1 x 10^-3 M, 2 x 10^-3 M and 3 x 10^-3 M respectively at 300K. The value of K_c for this equilibrium at the same temperature is

1) 1/6
2) 6
3) 1/36
4) 36

32. The equilibrium constant for the reversible reaction,
N₂ + 3H₂ ⇋2NH₃ is K and for reaction 1/2N₂ + 3/2H₂ ⇋ NH₃, the equilibrium constant is K’. The K and K’ related as:

1) K X K’ = 1 
2) K =K’
3) K’ = √K
4) K = √K’

33. For the reaction: N₂(g) + O₂(g) ⇋2NO(g), the equilibrium constant is K₁. The equilibrium constant is K₂ for the reaction:
2NO(g) + O₂(g) ⇋2NO₂(g). What is K for the reaction:
NO(g) ⇋ N₂(g) + O₂(g)?

34. A vessel of 1L capacity containing 1 mole of SO₃ is heated till a state of equilibrium is attained. 2SO₃(g) ⇋2SO2(g) + O₂(g)
At equilibrium, 0.6 moles of SO₂ had formed. The value of K is:

1) 0.18
2) 0.36
3) 0.45
4) 0.68

35. The value of equilibrium constant of the reaction,
Hl(g) ⇋1/2H₂(g) + 1/2I₂(g) is 8.0. The equilibrium constant of the reaction H₂(g) + I₂(g) ⇋2HI(g) will be:

1) 16
2) 1/8
3) 1/16
4) 1/64

36. If an inert gas is added in the reaction, N₂ + 3H₂ ⇋2NH₃ at constant volume, the its equilibrium

1. Remains unaffected
2. favours the backward reaction
3. favours the forward reaction
4. Increases the dissociation of reactants.

37. Densities of diamond and graphite are 3.5 and 2.3g/mL.
C(diamond) ⇋C(graphite) Δ_rH = -1.9kJ/mole
Favourable conditions for formation of diamond are

1. High pressure and low temperature
2. Low pressure and high temperature
3. High pressure and high temperature
4. Low pressure and low temperature

38. In Haber process, 30 litres of dihydrogen and 30 litres of dinitrogen were taken for reaction which yielded only 50% of the expected product. What will be the composition of gaseous mixture under the aforesaid condition in the end?

1. 20 lires ammonia, 20 litres nitrogen, 20 litres hydrogen
2. 10 lires ammonia, 25 litres nitrogen, 15 litres hydrogen
3. 20 lires ammonia, 10 litres nitrogen, 30 litres hydrogen
4. 20 lires ammonia, 25 litres nitrogen, 15 litres hydrogen

39. For the reaction, 2NO₂(g) ⇋N₂O₄(g), K_p/K_c is equal to

1) 1/RT
2) √RT
3) RT 
4) (RT)²

40. For the reaction, 2H₂(g) + O₂(g) ⇋2H₂O(g)
Which of the following fact holds good?

1. K_p = K_c
2. K_p > K_c
3. K_p < K_c
4. K_p and K_c cannot be correlated.

41. In a gaseous chemical equilibrium, K_c > K_p

1. if the forward reaction results in increasing number of molecules
2.If the forward reaction results in decreasing number of molecules
3. If there is no change in the number of molecules
4. None of the above cases.

42. 3O₂(g) ⇋2O3(g)
For the above reaction at 298K. K_c is found to be 3.0 x 10^-59. If the concentration of O₂ at equilibrium is 0.040M then concentration of O₃ in M is

1) 1.9 x 10^-63
2) 2.4 x 10³¹
3) 1.2 x 10²¹
4) 4.38 x 10^-32

43. The equilibrium concentrations of the species in the reaction A + B ⇋C + D are 2, 3, 10 and 6 molL^-1, respectively at 300K. ΔG^o for the reaction is
(R = 2cal/molK)

1) -137.26 cal
2) -1381.80 cal
3) -13.73 cal
4) 1372.60 cal

44. In which of the following equilibria, K_p and K_c are NOT equal?

1. PCl₅(g) ⇋PCl₃(g) + Cl₂(g)
2. H₂(g) + I₂(g) ⇋2HI(g)
3. CO(g) + H₂O(g) ⇋CO₂(g) + H₂(g)
4. 2BrCl(g) ⇋Br₂(g) + Cl₂(g)

45. For a reaction, N₂+ 3H₂ ⇋2NH₃, the value of K_c would depend upon

1. initial concentration of the reactants
2. pressure
3. temperature
4. all of these