Match the transformation in Column I with appropriate options in Column II. (A)...
Match the transformation in Column I with appropriate options in Column II.


Solution:
(A) CO2( s)⟶CO2( g)
It is just a phase transition (sublimation) as no chemical change has occurred. Sublimation is always endothermic. Product is gas, more disordered, hence Δs is positive.
(B) CaCO3( s)⟶CaO(s)+CO2( g)
It is a chemical decomposition, not a phase change. Thermal decomposition occur at the expense of energy, hence endothermic. Product contain a gaseous species, hence, ΔS>0.
(C) 2H⟶H2( g)
A new H−H covalent bond is being formed, hence, ΔH<0.
Also, product is less disordered than reactant, ΔS<0.
(D) Allotropes are considered as different phase, hence P(white, solid) →P(red, solid) is a phase transition as well as allotropic change.
Also, red phosphorus is more ordered than white phosphorus, ΔS<0.
It is just a phase transition (sublimation) as no chemical change has occurred. Sublimation is always endothermic. Product is gas, more disordered, hence Δs is positive.
(B) CaCO3( s)⟶CaO(s)+CO2( g)
It is a chemical decomposition, not a phase change. Thermal decomposition occur at the expense of energy, hence endothermic. Product contain a gaseous species, hence, ΔS>0.
(C) 2H⟶H2( g)
A new H−H covalent bond is being formed, hence, ΔH<0.
Also, product is less disordered than reactant, ΔS<0.
(D) Allotropes are considered as different phase, hence P(white, solid) →P(red, solid) is a phase transition as well as allotropic change.
Also, red phosphorus is more ordered than white phosphorus, ΔS<0.
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