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Molar heat capacity of CD(2)O (deuterate...

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`.

A

`-0.1 "cal"K^(-1)`

B

`-0.25 "cal"K^(-1)`

C

`-0.4"cal"K^(-1)`

D

`-0.15"cal"K^(-1)`

Text Solution

Verified by Experts

The correct Answer is:
D
`DeltaH` for cooling
`CD_(2)O=mSDeltaT=3.2/32xx14xx100=140` cal
`:.` Cooling is exothermic `Dletah=-140` cal
Now `DeltaS=(DeltaH)/T=-140/900=-0.15"cal"K^(-1)`
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