# Question #562d1

##### 1 Answer

#"20 dm"^3"/mol"#

Recall that *stoichiometric coefficients become the exponents* of each concentration (because each equilibrium reaction direction is an elementary reaction from kinetics).

#K_c = (["N"_2"O"_4])/(["NO"_2]^2)#

Always make sure you wrote down the problem correctly. You are actually given that

So:

#color(blue)(K_c) = ("0.2 M")/(("0.1 M")^2)#

#= "20 M"^1"/M"^2#

#= color(blue)("20 M"^(-1))# or

#color(blue)("dm"^3"/mol")# , since#1 - 2 = -1# for the exponents, and#"M"^(-1) = 1/"M" = 1/("mol"/"dm"^3) = "dm"^3/"mol"# .