Question

Incorrect Question 19 0/1 pts The value of A Sº for the catalytic hydrogenation of acetylene to ethene, C2H2(g) + H2(g) →C2H4 (g) is_ J/K.mol. Use the following thermodynamic quantities for selected substances at 298.15 K (25°C). Substance AHºf (kJ/mol) AG°f (kJ/mol) S (J/K-mol) 2.84 Carbon C(s, diamond) 1.88 C(s, graphite) 0 C2H2(g) 226.7 C2H4 (g) 52.30 C2H6 (g) -84.68 CO(g) -110.5 CO2 (g) -393.5 209.2 68.11 -32.89 -137.2 -394.4 2.43 5.69 200.8 219.4 229.5 197.9 213.6 Hydrogen H2(g) 0 130.58 Oxygen O2(g) H20 (1) 0 205.0 69.91 -285.83 -237.13 +112.0
Please explain the correct answer to both questions. Thank you!

Answer 1

Q.N0-19. The given reaction is C2H2(g) + H2(g) ----------> C2H4(g)

$\Delta$s0rxn = S0 products - s0 reactants

       = S0 C2H4(g) - s0 C2H2(g) - s0 H2(g)

       = 219.4 -200.8-130.58

       = -111.98 $\approx$    -112 J/K-mole

Q.N0-24. Thermodynamics does not give information about the speed of a reaction but it gives information about the spontaneity of a reaction, direction of spontaneous reaction and extent of reaction and the value of equilibrium constant and the temperature at which reaction is spontaneous.

If $\Delta$ G = -ve, the reaction is spontaneous reaction and the free energy and equilibrium constant related by $\Delta$ G = -RTlnK