Acetylene, C2H2, can be converted to ethane, C2H6, by a process known as hydrogenation. The reaction is C2H2(g)+2H2(g)?C2H6(g)
Given the following data, what is the value of Kp for this reaction?
Substance ΔG∘f
(kJ/mol)
C2H2(g) 209.2
H2(g) 0
C2H6(g) -32.89

Respuesta :

Answer : The  value of [tex]K_p[/tex] for this reaction is, [tex]2.73\times 10^{42}[/tex]

Explanation :

The given chemical reaction is:

[tex]C_2H_2(g)+2H_2(g)\rightarrow C_2H_6(g)[/tex]

Now we have to calculate value of [tex](\Delta G^o)[/tex].

[tex]\Delta G^o=G_f_{product}-G_f_{reactant}[/tex]

[tex]\Delta G^o=[n_{C_2H_6(g)}\times \Delta G^0_{(C_2H_6(g))}]-[n_{C_2H_2(g)}\times \Delta G^0_{(C_2H_2(g))}+n_{H_2(g)}\times \Delta G^0_{(H_2(g))}][/tex]

where,

[tex]\Delta G^o[/tex] = Gibbs free energy of reaction = ?

n = number of moles

[tex]\Delta G^0_{(C_2H_6(g))}[/tex] = -32.89 kJ/mol

[tex]\Delta G^0_{(C_2H_2(l))}[/tex] = 209.2 kJ/mol

Now put all the given values in this expression, we get:

[tex]\Delta G^o=[1mole\times (-32.89kJ/mol)]-[1mole\times (209.2kJ/mol)+2mole\times (0kJ/mol)][/tex]

[tex]\Delta G^o=-242.09kJ/mol[/tex]

The relation between the equilibrium constant and standard Gibbs, free energy is:

[tex]\Delta G^o=-RT\times \ln K_p[/tex]

where,

[tex]\Delta G^o[/tex] = standard Gibbs, free energy

R = gas constant  = 8.314 J/L.atm

T = temperature  = 298 K

[tex]K_p[/tex] = equilibrium constant = ?

Now put all the given values in this expression, we get:

[tex]-242.09kJ/mol=-(8.314J/L.atm)\times (298K)\times \ln K_p[/tex]

[tex]K_p=2.73\times 10^{42}[/tex]

Thus, the value of [tex]K_p[/tex] for this reaction is, [tex]2.73\times 10^{42}[/tex]