For the reaction HCNONH_2(g) NH_3(g) + CO(g), K_c =4.84 at 400k. If delta H degr
ID: 1048696 • Letter: F
Question
For the reaction HCNONH_2(g) NH_3(g) + CO(g), K_c =4.84 at 400k. If delta H degree. For this reaction is 29 KJ/mol, find K_c at 500 k. 27 10.3 0.17 5.8 0.88 predict the normal boiling point of triethylborane (C_6H_15B)using the following data: C_6H_15B(I) C_6 H_15 B(g) delta H degree _f(25degreeC) -194.6KJ/mol -157.7KJ/mol delta G degree _f (25 degree C) 9.4KJ/mol 16.1KJ/mol 256 degree C 92 degree C -21 degree C 21 degree C 365 degree C which one of the following reactions will occur spontaneously at standard - state conditions and 25 degree C?
Explanation / Answer
1.
Standard Gibbs free energy change for vaporization, deltaG = -157.7-(-194.6) =36.9 Kj/mol
Standard Enthalpy change for vaporization , deltaH= 16.1- 9.4= 6.7 Kj/mol
detaG =deltaH- TdeltaS
deltaS = (36.9-6.7)/298.15 =0.1012 Kj/mol
at boiling point deltaG= deltaH- TdeltaS = 0
36.9- T*0.1012=0 ( assuming entropy to be temperature independent)
T= 364K = 91.4 deg.c. Close answer is 92 deg.c ( B is correct)
2. Standard Gibbs free energy change for vaporization, deltaG = -157.7-(-194.6) =36.9 Kj/mol
Standard Enthalpy change for vaporization , deltaH= 16.1- 9.4= 6.7 Kj/mol
detaG =deltaH- TdeltaS
deltaS = (36.9-6.7)/298.15 =0.1012 Kj/mol
at boiling point deltaG= deltaH- TdeltaS = 0
36.9- T*0.1012=0 ( assuming entropy to be temperature independent)
T= 364K = 91.4 deg.c. Close answer is 92 deg.c ( B is correct)
3. CU(s)+2H+ --->Cu+2 +H2 Eo=-0.34 gibss free energy= -nFE sicne gibbs free energy is +ve, the reaction is not spontaneous
for the reaction Ni+2 +2Fe+2--->Ni+2Fe+3 EO= 1V, sicne Eo is +ve, deltaG is -ve and the process is spontaneous
for the reaction Mg+2 +Ca--->Mg+ Ca+2
Mg+2 +2e--- >Mg Eo= -2.38 and Ca--->Ca+2 +2e- Eo= 2.76
hecne Mg+2 +Ca --->Ca+2 + Mg Eo= 2.76-2.38= 0.38v
since Eo is +ve deltaG is -ve and spontaneous
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