MHT CET202522 Apr 2025Evening ShiftChemistryThermodynamics (C)Actual
Identify from following reactions that exhibits negative work done.
Options
- A2 H ₂ O _ 2( ) 2 H ₂ O _ ( ) + O _ 2( ~g )
- BNH _ 3( ~g ) + HCl _ ( g ) NH ₄ Cl _ ( s )
- CH _ 2( ~g ) + Cl _ 2( ~g ) 2 HCl _ ( g )
- DN _ 2( ~g ) +3 H _ 2( ~g ) 2 NH _ 3( ~g )
Correct answer
A. 2 H ₂ O _ 2( ) 2 H ₂ O _ ( ) + O _ 2( ~g )
Step-by-step solution
Negative work occurs when the system expands at constant pressure, which requires a positive change in gaseous moles. The work done is given by W = - n_g RT , where n_g is the change in the number of moles of gaseous species. For reaction A: 2 H ₂ O _ 2( ) 2 H ₂ O _ ( ) + O _ 2( g ) Gaseous products: 1, reactants: 0, so n_g = 1 > 0 . Hence, W For reaction B: NH _ 3( g ) + HCl _ ( g ) NH ₄ Cl _ ( s ) Gaseous products: 0, reactants: 2, so n_g = -2 0 . For reaction C: H _ 2( g ) + Cl _ 2( g ) 2 HCl _ ( g ) Gaseous pro