Question

Use the References to access important values if needed for this question. Consider the reaction Fe(s) + 2 HCl(aq) FeCl2(s) + H2(g) Using the standard thermodynamic data in the tables linked above, calculate the equilibrium constant for this reaction at 298.15K. ANSWER:

Answer 1

Answer – We are given, reaction –

Fe(s) + 2 HCl(aq) -----> FeCl₂(s) + H₂(g)

First we need to calculate the ∆G^orxn

We know,

ΔG^o_rxn = ∑ ΔG^o_f of product – ∑ ΔG^o_f of reactant

= [ (ΔG^o_f FeCl₂(s)) + (ΔG^o_f H₂(g) )] – [ ΔG^o_f Fe (s) + 2*ΔG^o_f HCl(aq)]

= (-302.34 + 0.00) – ( 0.00 + 2*-131.17)

= -42 kJ/mol

Now we know,

ΔG^o = -RTlnK

-4.2*10⁴ J = -8.314 J/mol.K * 298.15 K * ln K

So, ln K = -4.2*10⁴ J / -8.314 J.mol^-1 .K^-1 * 298.15 K

              = 16.94

By taking antiln from both side

K = 2.28*10⁷

The equilibrium constant for this reaction at 298.15K is 2.28*10⁷