Question

A reaction flask contains H2(g), I2(g) and HI(g) at equilibrium at a constant temperature, according to the following reaction: H2 (g) + I2 (g) __________> 2HI (g)
Measurements gave the concentrations as [H2] = 0.102M, [I2] = 0.00183M and [HI] = 0.0963M

(a) Write the Equilibrium Constant expression, Kc for this specific reaction.
(b) Calculate the value of Kc for this temperature. Kc ___________
(c) Is this a homogeneous or heterogeneous reaction? _____________ Explain your choice, what the term means.

Answer 1

Answer:

a. [HI]² / [I₂] . [H₂]

b. Kc = 46.9

c. This is an homogeneous reaction

Explanation:

The equilibrium is this:

            H₂ (g)   +      I₂ (g)      ⇄   2HI (g)

Eq.      0.102M    0.00183M        0.0963M

The expression for Kc will be:

Kc = [HI]² / [I₂] . [H₂]

Kc = 0.0963² / 0.00183 . 0.102

Kc = 46.9

The reaction is homegeneous, because all the reactants and the product are at the same phase. In this case, as the reaction is homogeneous, the speed of reaction is not affected by the exposed surface area.

If it was an heteregeneous reaction,  it would depend on the area of ​​the surface exposed to the mixture of  reaction. The heterogeneous reaction are in a different phase, for example a catalyst in a different phase as the reactants.