MHT CET Medical202624 April 2026Evening ShiftChemistryThermodynamics (C)Actual
Identify from following reactions that it takes place with H = U .
Options
- ACO ₂(g) + H ₂(g) CO (g) + H ₂ O (g)
- BN ₂(g) + 3 H ₂(g) 2 NH ₃(g)
- CCO (g) + 1 2 O ₂(g) CO ₂(g)
- DH ₂(g) + 1 2 O ₂(g) H ₂ O (l)
Correct answer
A. CO ₂(g) + H ₂(g) CO (g) + H ₂ O (g)
Step-by-step solution
The relationship between enthalpy change ( H ) and internal energy change ( U ) is given by: H = U + n_g RT For H = U , the change in the number of moles of gaseous species ( n_g ) must be zero. n_g = moles of gaseous products - moles of gaseous reactants Evaluating n_g for the given reactions: For CO ₂(g) + H ₂(g) CO (g) + H ₂ O (g) : n_g = (1 + 1) - (1 + 1) = 0 For N ₂(g) + 3 H ₂(g) 2 NH ₃(g) : n_g = 2 - (1 + 3) = -2 For CO (g) + 1 2 O ₂(g) CO ₂(g) : n_g = 1 - (1 + 1 2 ) = -0.5 For H ₂(g) + 1 2 O ₂(g) H ₂ O (l) :