# Is #K_c# dependent on initial concentrations?

##### 1 Answer

** initial** concentrations because that's not how it is defined. It is only for

**concentrations.**

*equilibrium*The constant for ** initial** concentrations (or "current" concentrations) is reserved for the

**Reaction Quotient**

Suppose we have this general reaction:

#color(green)(2)A + B rightleftharpoons color(green)(3)C + color(green)(2)D#

It is always defined like this for this reaction:

#Q = (prod_j [P_j]_0^color(green)(nu_(P_j)))/(prod_i [R_i]_0^color(green)(nu_(R_i)))#

#K_C = (prod_j [P_j]_"eq"^color(green)(nu_(P_j)))/(prod_i [R_i]_"eq"^color(green)(nu_(R_i)))# where the

#prod# symbol just means multiply the numbers that come after it, square brackets denote concentration (or if you know what activities are, use activities; no, I don't mean the activity series),#0# means "initial",#R_i# is each reactant of index#i# ,#P_j# is each product of index#j# , and#nu# is the stoichiometric coefficient.

So, you can write this as:

#Q = ([C]_0^color(green)(3)[D]_0^color(green)(2))/([A]_0^color(green)(2)[B]_0)#

#K_C = ([C]_"eq"^color(green)(3)[D]_"eq"^color(green)(2))/([A]_"eq"^color(green)(2)[B]_"eq")#