1.

Urea on hydrolysis produces ammonia and carbon dioxide. The standard entropies of urea, H_2O , CO_2 , NH_3are 173.8,70,213.5 and 192.5 "J mole"^(-1) K^(-1)respectively. Calculate the entropy change for this reaction.

Answer»

Solution :`S^0"(UREA)=173.8 "J mol"^(-1) K^(-1)`
`S^0(H_2O)=70 "J mol"^(-1)K^(-1)`
`S^0(CO_2)=213.5 "J mol"^(-1) K^(-1)`
`S^0(NH_3)=192.5 "J mol"^(-1) K^(-1)`
`NH_2-CO-NH_2+H_2O to 2NH_3+CO_2`
`DeltaS_r^0 =sum (S^0)_"products" -sum (S^0)_"reactants"`
`DeltaS_r^0=[2S^0(NH_3)+S^0(CO_2)]-[S^0"(urea)"+S^0(H_2O)]`
`DeltaS_r^0`=[ 2 x 192.5 + 213.5 ]-[173.8 +70 ]
`DeltaS_r^0`=[598.5]-[243.8]
`DeltaS_r^0=354.7 "J mol"^(-1) K^(-1)`


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