Concept explanation

[aless_wu]

I'm having trouble understanding this concept dealing with reaction quotients.
For example in #13 of the Ch. 11 problems, the reaction quotient is (1)/(BCl3)^2 instead of (B2Cl4)(Hg2Cl2)/(Hg)^2 (BCl3)^2 . How did it reduce to that? The same happens in part b and other problems.

[Sarah_Wilen]

Remember that the only phase species that are in the equilibrium equation would be aqueous and gaseous substances. Solids and liquids don't participate in the equilibrium equation because they don't affect it. Pure solids and liquids are disregarded and their value is kept as 1 as to not affect the equilibrium constant.

A homogeneous equilibrium has everything present in the same phase. A heterogeneous equilibrium has things present in more than one phase. The reaction below is an example of a heterogeneous equilibrium.

The reaction for #13 part a is 2 BCl3 (g) + 2Hg (l) --> B2Cl4 (s) + Hg2Cl2 (s)
-We omit Hg, B2Cl4, and Hg2Cl2 because they are in liquid, solid, and solid phases, which we know don't participate
-The resulting equilibrium equation is 1/(BCl3)^2