Purification of Ni metal can be facilitated by its ability to react with carbon

ID: 925373 • Letter: P

Question

Purification of Ni metal can be facilitated by its ability to react with carbon monoxide.

Ni(s) + 4CO(g) --> Ni(CO)4(g)

Substance: Ni(s) CO(g) Ni(CO)4(g)

S°(J/K•mol): 30.1 197.9 410.6

DH° (kJ/mol): 0 -110.5 -602.9

What is DG° for this reaction? (If I need to use the temperature, would I assume 25 celsius? If so, what would be the correct answer?)

A) –437.9 kJ/K•mol

B) +437.9 kJ/K•mol

C) +38.4 kJ/K•mol

D) –38.4 kJ/K•mol

E) –438.2 kJ/K•mol

A) –437.9 kJ/K•mol

B) +437.9 kJ/K•mol

C) +38.4 kJ/K•mol

D) –38.4 kJ/K•mol

E) –438.2 kJ/K•mol

Solution :-

Ni(s) + 4CO(g) --> Ni(CO)4(g)

Need to first calculate the Delta H and delta S reaction using the standard values

Delta H rxn = sum of delta H product – sum of delta H reactant

=[Ni(CO)4*1] – [ (Ni*1)+(CO*4)]

= [-602.9*1] – [(0*1)+(-110.5*4)]

= -160.9 kJ

Now lets calculate the delta S rex

Delta S rxn = sum of delta S product – sum of delta S reactant

=[Ni(CO)4*1] – [ (Ni*1)+(CO*4)]

= [410.6*1]-[(30.1*1)+(197.9*4)]

= -411.1 J per mol K

Lets convert it to kJ

-411.1 J per K * 1 kJ / 1000 J = -0.4111 kJ / mol K

Now lets calculate the delta G

Delta G= Delta H – (T*delta S)

= -160.9 kJ – (298 K * (-0.4111 kJ))

= -38.4 KJ

So the correct answer is option D

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