Predict which of the following reaction(s) has a negative entropy change 
$\mathrm{I}) {\mathrm{CH}}_4(\mathrm{g})+2{\mathrm{O}}_2(\mathrm{g})\to {\mathrm{CO}}_2(\mathrm{g})+2{\mathrm{H}}_2\mathrm{O}(\mathrm{\ell })$
$\mathrm{II}) {\mathrm{NH}}_3(\mathrm{g})+\mathrm{HCl}(\mathrm{g})\to {\mathrm{NH}}_4\mathrm{Cl}(\mathrm{s})$
$\mathrm{III}) 2{\mathrm{KClO}}_4(\mathrm{s})\to 2{\mathrm{KClO}}_3(\mathrm{s})+{\mathrm{O}}_2(\mathrm{g})$

$\mathrm{I}) {\mathrm{CH}}_4(\mathrm{g})+2{\mathrm{O}}_2(\mathrm{g})\to {\mathrm{CO}}_2(\mathrm{g})+2{\mathrm{H}}_2\mathrm{O}(\mathrm{\ell })$

In this reaction we can see that water molecules are forming which have low entropy that the gas molecules.

$\mathrm{II}) {\mathrm{NH}}_3(\mathrm{g})+\mathrm{HCl}(\mathrm{g})\to {\mathrm{NH}}_4\mathrm{Cl}(\mathrm{s})$

In this reaction we can see that gas molecules are forming  solid which have least entropy .