Answer:
The correct answer is B.
Explanation:
Heterogeneous equilibrium is that in which reagents and products are present in more than one phase.
When the reaction is carried out in a closed container, three equilibrium phases are present: solid magnesium oxide, solid magnesium sulfate and gaseous sulfur trioxide.
Hence, the equilibrium contant is given by:
The concentrations in the equilibrium equation are the relationships of the real concentrations between the concentrations in the standard state. Since the standard state of a pure solid is the pure solid itself, the ratio of concentrations for a pure solid is equal to one.
Now, we analyse each statement:
I) As the reaction is endothermic (ΔH>0), increasing the temperature shifts the balance to the right because excess heat will be used to form more products.
II) Increasing the volume will decrease the concentration of SO₃, so Q>K and then this shifts the balance to the left.
III) As it is a heterogeneous balance, adding MgO will not affect the balance.
IV) Removing SO3 will decrease its concentration and therefore the reaction equilibrium will shift to the left.