calculating k
 

i need to know how to calculate the K for and equlilbrium reaction when i'm missing one of the equilibrium concentrations for one of the products. i've got Ag+ + Fe2+ = Ag + Fe3+ ( i don't know how to do that little double arrow).
anywayz, i have conc's for all but Ag, one of the products.

You don't need it
 

For an equilibrium expression, remember that what is used in the equation can be either concentrations in solution or partial pressures. Here, it would be concentrations in mol/L (molarity). This is a redox equation which is balanced, but the one product you don't have a concentration for, Ag, is a solid. As such, it won't have a concentration, and doesn't show up in the equilibrium expression.

cheers
 

Of course. We've only just started this component of the course, so some of these concepts are still sinking in. You're absolutely right. Thank you very much. So, any substance in solid (elemental?) form isn't included in the expression? Also, I know water isn't included in these expressions, because it's a "whole substance". It has it's own K. What about other liquids, ie liquid methane?