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How do I find out initial amounts of a equilibrium problem if one or some of them are not given ? Ex: Equilibrium is established in a 2.50-L flask at 250 degree celcius for the reaction: PCl5(g) -> PCl3(g) + Cl2(g) Kc= 3.8x10^-2 How many moles of each molecule is present, if 0.550mol of each PCl5 and PCl3 was initially introduced into the flask? .. thanks