Gibbs energy change and equilibrium constant
- The equilibrium concentrations of the species in the reaction A + B ⇌ C + D are 2, 3, 10 and 6 mol L^-1, respectively at 300 K. Δ G^° for the reaction is (R = 2 cal / mol K) Answer: 4. -1381.80 cal Key idea: Δ G^° = -2.303 RTlog K . K = [C][D]/[A][B] = 10 × 6/2 × 3 = 10 , so log K = 1 . Δ G^° = -2.303 × 2 × 300 ×... 1
- Hydrolysis of sucrose is given by the following reaction.Sucrose + H_2O ⇌ Glucose + FructoseIf the equilibrium constant (K_c) is 2×10^13 at 300 K, the value of Δ_rG^ at the same temperature will be : Answer: 1. -8.314 J mol ⁻¹ K ⁻¹×300 K ×ln(2×10¹³) Standard Gibbs energy and equilibrium constant are related by Δ_rG^ominus=-RTln K . Substi... 1
- Considering Ellingham diagram, which of the following metals can be used to reduce alumina ? Answer: 2. Mg In an Ellingham diagram, a metal can reduce an oxide only if its own oxide-formation line lies below that of the oxide to be r... 1
- For a given reaction, Δ H = 35.5\ kJ\ mol^-1 and Δ S = 83.6\ JK^-1mol^-1. The reaction is spontaneous at : (Assume that Δ H and Δ S do not vary with temperature) Answer: 1. T > 425 K Key idea: a reaction is spontaneous when Δ G = Δ H - TΔ S < 0 . For Δ G<0 : T > Δ H/Δ S . T > dfrac35.5×10³\ mathrmJ mo... 1
- Consider the following liquid - vapour equilibrium.Liquid ⇌ VapourWhich of the following relations is correct ? Answer: 4. dln P/dT = Δ H_v/RT² Key idea: this is the Clausius-Clapeyron equation for liquid-vapour equilibrium: dln P/dT=Δ H_v/RT² Vapour p... 1