3.1.6.2 Equilibrium constant Kc for homogenous systems

Question 1

How do you work out Kc problems?

Answer 1

1. Draw a table, label it intial number of moles, change in moles, equilibrium moles, equilibrium concentration for each one
2. Put in all information. Change is parallel to the number of moles in the equation
3. Calculate equilibrium concentration
4. State the expression of Kc: reaction components in [ ]
5. Substitute concentrations into the equation
6. Work out the units for Kc and add them to your answer

Question 2

In what scenarios does Kc have no units?

Answer 2

When there are an equal number of moles on either side of the reaction which makes them cancel out

Question 3

What is the equation for Kc?

Answer 3

A + 2B = C + 2D
[C] [D]2
———-
[A] [B]2

Question 4

Why, in some cases, would you not need to know the total volume to find Kc?

Answer 4

If there is an equal number of moles on both sides of the reaction