CaCO_(3) exists in two forms,calcite and aragonite. The conversion of 1 mole of calcite to aragonite is accompanied by internal energy change equalto +0.21 kJ. Given that the densities of calcite and aragoniteare 2.61 gcm^(-3) and 2.93 g cm^(-3) respectively , calculate the enthalpy change at the pressureof1.0bar.

CaCO_(3) exists in two forms,calcite and aragonite. The conversion of

1.	CaCO_(3) exists in two forms,calcite and aragonite. The conversion of 1 mole of calcite to aragonite is accompanied by internal energy change equalto +0.21 kJ. Given that the densities of calcite and aragoniteare 2.61 gcm^(-3) and 2.93 g cm^(-3) respectively , calculate the enthalpy change at the pressureof1.0bar.
Answer» Solution :`DeltaH= DELTAU + P DeltaV` Here, `DeltaU =+ 0.21kJmol^(-1)=0.21xx 10^(3)J mol^(-1)= 210J mol^(-1)` `P =1 ` bar `=10^(5)` P `DeltaV =`Molar VOLUME of aragonite `-` Molar volume of calcite `= ( 100)/( 2.93)- (100)/( 2.71) cm^(3) mol^(-1)``( :'` Molar mass of`CaCO_(3) = 100 G mol^(-1))` `= 100 (( 1)/( 2.93 )- (1)/( 2.71)) =100 xx ( -0.22)/(2.93xx2.71) = -2.77 cm^(3) mol^(-1) = - 2.77 xx 10^(-6) m^(3) mol^(-1)` `:. DeltaH = 210 +10^(5) ( - 2.77 xx 10^(-6))=210- 0. 277 J = 209. 72 J mol^(-1)`