NEETChemistryThermodynamics (C)
Match List-I with List-II for the relationship between enthalpy change ( H ) and internal energy change ( U ) at constant temperature. List-I (Reaction) List-II (Relationship) (A) H ₂( g ) + I ₂( g ) 2 HI ( g ) (I) H = U - 2RT (B) PCl ₅( g ) PCl ₃( g ) + Cl ₂( g ) (II) H = U - RT (C) N ₂( g ) + 3 H ₂( g ) 2 NH ₃( g ) (III) H = U (D) 2 CO ( g ) + O ₂( g ) 2 CO ₂( g ) (IV) H = U + RT Choose the correct answer from the
Options
- A(A)-(III), (B)-(I), (C)-(IV), (D)-(II)
- B(A)-(III), (B)-(II), (C)-(I), (D)-(IV)
- C(A)-(IV), (B)-(III), (C)-(II), (D)-(I)
- D(A)-(III), (B)-(IV), (C)-(I), (D)-(II)
Correct answer
D. (A)-(III), (B)-(IV), (C)-(I), (D)-(II)
Step-by-step solution
The relationship between enthalpy change and internal energy change is given by H = U + n_g RT , where n_g is the change in the number of moles of gaseous species. For reaction (A): H ₂( g ) + I ₂( g ) 2 HI ( g ) n_g = 2 - (1 + 1) = 0 Therefore, H = U Matches with (III). For reaction (B): PCl ₅( g ) PCl ₃( g ) + Cl ₂( g ) n_g = (1 + 1) - 1 = +1 Therefore, H = U + RT Matches with (IV). For reaction (C): N ₂( g ) + 3 H ₂( g ) 2 NH ₃( g ) n_g = 2 - (1 + 3) = -2 Therefore, H = U - 2RT Matches with (I). For reaction (D)