Question

Mercury(I) oxide decomposes into elemental mercury and elemental oxygen:.

(a)Write the equilibrium-constant expression for this reaction in terms of partial pressures.

(b) Suppose you run this reaction in a solvent that dissolves elemental mercury and elemental oxygen. Rewrite the equilibrium-constant expression in terms of molarities for the reaction, using (solv) to indicate solvation.

Answer 1

(a)

The equation for the decomposition of mercury (I) oxide into elemental mercury and oxygen is:

 

2Hg2O(s) → 4Hg(l) + O2(g)

 

The equilibrium constant expression for this reaction in terms of partial pressures is:

Kp = PO2

 

Since the other substances are pure solid, pure liquid their concentrations (pressures as T is constant) does not appear in the equilibrium constant expression.

 

(b)

When the above chemical reaction runs in a solvent that dissolves elemental mercury and elemental oxygen. The chemical equation is:

2Hg2O(s) → 4Hg(solv) + O2(solv)

 

The equilibrium constant expression for this reaction is:

Kc = [Hg(solv)]4[O2(solv)]

 

Because H2O is pure solid, its concentration does not appear in the equilibrium constant expression.

(a)

The equation for the decomposition of mercury (I) oxide into elemental mercury and oxygen is:

 

2Hg2O(s) → 4Hg(l) + O2(g)