Match the transformation in Column I with appropriate options in Column II.
Match the transformation in Column I with appropriate options in Column II.
(A) p,q,r,s, (B) r,s, (C) t, (D) p,q
(A) p,s, (B) p,s, (C) s, (D) p,q,s
(A) p,s, (B) q,r, (C) s, (D) p,q
(A) p,r,s, (B) r,s, (C) t, (D) p,q,t
Solution
(A) $\mathrm{CO}_2(\mathrm{~s}) \longrightarrow \mathrm{CO}_2(\mathrm{~g})$
It is just a phase transition (sublimation) as no chemical change has occurred. Sublimation is always endothermic. Product is gas, more disordered, hence $\Delta s$ is positive.
(B) $\mathrm{CaCO}_3(\mathrm{~s}) \longrightarrow \mathrm{CaO}(\mathrm{s})+\mathrm{CO}_2(\mathrm{~g})$
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, $\Delta S>0$.
(C) $2 \mathrm{H} \longrightarrow \mathrm{H}_2(\mathrm{~g})$
A new $\mathrm{H}-\mathrm{H}$ covalent bond is being formed, hence, $\Delta H < 0$.
Also, product is less disordered than reactant, $\Delta S < 0$.
(D) Allotropes are considered as different phase, hence $\mathrm{P}_{\text {(white, solid) }} \rightarrow \mathrm{P}_{\text {(red, solid) }}$ is a phase transition as well as allotropic change.
Also, red phosphorus is more ordered than white phosphorus, $\Delta S < 0$.
