) Calculating a reactant from Kc:
• This time you are told Kc at the start and initial moles and equilibrium moles.
• Remember to convert to equilibrium concentrations.
6.00 moles of PCl3 is mixed with an unknown amount of Cl2. 2.00 moles of PCl5 is made.
How many moles of Cl2 was added? Kc = 20. The experiment was carried out in a 2dm3
flask.
Reaction PCl3(g) + Cl2(g) PCl5(g)
Stoichiometry 1 1 1
Initial n moles 6.00 x 0.0
Reacted
n moles at equilibrium 2.00
[Eq]
• Write the equilibrium expression, put in the values, calculate Kc and work out the units:
I've worked out the equilibrium expression but what would the answer to the question?