1.

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»

`-0.1 "cal"K^(-1)`
`-0.25 "cal"K^(-1)`
`-0.4"cal"K^(-1)`
`-0.15"cal"K^(-1)`

Solution :`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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