Assertion:The change in entropy during melting of ice is negligible in comparison to change in entropy during vaporisation.
Reason:The volume occupied by solid and liquids is too less in comparison to volume occupied by gas.

Options

A. If both assertion and reason are true and the reason is the correct explanation of the assertion.
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.
C. If assertion is true but reason is false.
D. If the assertion and reason both are false.

Answer

A

Explanation

The change in entropy during melting of ice `Delta S_("fus")= (Delta H_("fus"))/(T_(f)) = (Delta E_("fus") + P. Delta V_("fus"))/(T_(f))`
The change in entropy during vapourisation of water
`Delta S_("vap") = (Delta H_("vap"))/(T_(b))= (Delta E_("vap") + P. Delta V_("vap"))/(T_(b))`
Now `Delta V_("vap") gt gt Delta V_("fus"), Delta E_("vap") gt Delta E_("fus")`
Thus `Delta H_("vap") gt gt Delta H_("fus")`
`T_(f) = 0^(@)C = 273K, T_(b)= 100^(@)C= 373K`
`T_(b) gt T_(f)`, but the effect of denominator will be less comparison to the increase in numerator so `Delta S_("vap") gt gt Delta S_("fus")`
Hence reason is the correct explanation for assertion.