Question

	HgO(s)	Hg(g)	O2(g)
Enthaply Delta H kj/mol	-90.8	61.3
Entropy Delta S   j/mol. K	70.3	174.9	205.0

Above is a table of thermodynamics date for the chemical species in the reaction: 2HgO(s) ----> 2Hg(g)+ O2(g) at 25 C

A) Calculate the molar entropy of reaction at 25 C

B) Calculate the standard Gibbs free enregy of the reaction at 25 C given that the enthaply of reaction at 25 C is 304.2 Kj/mol

C)Calculate the equilibrium constant for the reaction at 25 C

D) Estimate the temperature where the decomposition of mercury (II) becomes readily favored

E) Calculate the Gibbs free energy of reaction at 298 K with an oxygen partial pressure of 30.0 atm and an Hg partial pressure at .100 atm

Answer 1

A)

S = Sproducts - Sreactants

= (174.9 + 205 ) -70.3

= 309.6 J / K mol

B)

H = 304 .2 kJ / mol

G = H - T S

= 304.2 - 298 x 309.6 x10^-3

= 212 kJ / mol

C )

G = - R T ln Keq

212 = - 8.314 x 10^-3 x 298 x ln Keq

Keq = 7.38 x 10^-28

D)

G = H - T S

G < 0 the reaction is favoured

H - T S < 0

304.2 < T x 309.6 x10^-3

982.6 K < T

temperature at 982.6 K above the reaction is favoured

E)

Kp = P²_Hg P_O2   = 0.1 ^2 x 30

Kp = 0.3

G = -RT ln Kp

= - 8.314 x 10^-3 x 298 x ln 0.3

= 2.98 kJ / mol