alleryThe relation between $\Delta H$ and $\Delta U$ for a reaction involving gases is:
A$\Delta H = \Delta U \cdot \Delta n_g R T$
B$\Delta H = \Delta U - \Delta n_g R T$
C$\Delta H = \Delta U + \Delta n_g R T$
D$\Delta H = \Delta U / \Delta n_g$
Answer & Solution
Correct answer: C. $\Delta H = \Delta U + \Delta n_g R T$
From the definition $H = U + pV$ and the ideal-gas relation $pV = n_g R T$, $\Delta H = \Delta U + \Delta(pV) = \Delta U + \Delta n_g R T$ at constant $T$, where $\Delta n_g$ is (moles of gaseous products) $-$ (moles of gaseous reactants).
For reactions with $\Delta n_g = 0$, $\Delta H = \Delta U$.
Keep practising Unit 6A1: Heat Transfer and Calorimetry
Browse all Unit 6A1: Heat Transfer and Calorimetry questions for JEE Advanced, or explore more Chemistry topics.
Related questions
For an adiabatic process, the first law of thermodynamics reduces to:Hess's law of constant heat summation is a direct consequence of:The relationship between $\Delta G^\circ$ and the equilibrium constant $K$ for a chemical A reaction is found to have $\Delta H = +30\,\text{kJ mol}^{-1}$ and $\Delta S = +100\,\teAt constant temperature and pressure, the criterion for a process to be **spontaneous** isWhich of the following is **always** true for a spontaneous process in an isolated system?The standard enthalpy of neutralisation of any strong acid by any strong base in dilute aqThe standard enthalpy of formation $\Delta_f H^\circ$ of any element in its most stable fo