Molar heat capacity of `CD_(2)O` (deuterated form of formaldehyde) at constant pressure in `9 cal mol^(-1) K^(-1) at 1000K`. Calculate the entropy change associated with cooling of `3.2 g` of `CD_(2)O` vapour from `1000 to 900K`.

Answer

`-0.1555 cal//"deg"`

Explanation

`Delta H` for the colling of
`CD_(2)O = m S Delta T = (3.2)/(32) xx 14 xx 100 = 140 cal`
`:.` Cooling is exothermic `Delta H = -140 cal`
Now, `Delta S = (Delta H)/(T) = - (140)/(900) = -0.1555 cal "deg"^(-1)`