S r = Σ (S ) products – Σ (S ) reactants D S r = [ S (NH ) + S (CO )] 11th Std Chemistry 11th Std Chemistry - - - - – [S (urea) + S (H O)] D S r = [ × . + . ] – [ . + ] D S r = [ .
] – [ . ] D S r = . J mol – K – . Solution: Given: T b = K D H vap = 39840 J mol – D S v = ?
∆ = ∆ ∆ ∆ S H S S J K mol v vap b v v 39840 . Solution: Given: D H = – kJ mol – = –10000 J mol – D S = – J K – mol – T = K D G = ? D G = D H – T D S D G = – kJ mol – – K × (–20x10 - ) kJ K – mol – D G = (– + ) kJ mol – D G = – kJ mol – At K D G = – kJ mol – – K × (–20x10 - ) kJ K – mol – D G = (– + ) kJ mol – D G = + kJ mol – The value of ∆G is negative at 300K and the reaction is spontaneous, but at 600K the value ∆G becomes positive and the reaction is non spontaneous. EVALUATION I Choose the best answer: .
(b) D H . (d) decrease in free energy . (b) q = . (d) = .
(a) w = – D U . (d) mass volume . (a) – J . (b) negative .
(b) – . kcal . (a) graphite is more stable than diamond . (d) – kJ .
(d) frictional energy . (d) D H < D U .