7.4.A.1 Determining Equilibrium Constants from Experimental Measurements: 

1. Measuring Concentrations or Partial Pressures:

i. Concentrations:
– Spectrophotometry: Uses absorbance to find concentration.
– Titration: Adds a known reactant to find concentrations.
– Conductivity Measurements: Uses electricity to measure changes in ion concentration.

ii. Partial Pressures (Gaseous Systems):
– Manometry: Measures pressure of gas within a closed container.
– Gas Chromatography: Qualifies and analyzes components of mixtures of gases.
– Ideal Gas Law: Gives pressure in terms of gas concentration to be applied for equilibrium calculations.
iii. General Approach:
– Sampling & Analysis: Regular sampling and analysis by the above process.
– Computational Methods: Applied for complicated systems to determine the equilibrium concentrations.

2. Calculating Equilibrium Constants (Kc, Kp):

i. Write the Balanced Equation:
For the reaction aA+bB⇌cC+dD the equilibrium expression is:

$$K_c = \frac{[C]^c [D]^d}{[A]^a [B]^b} \quad \text{or} \quad K_p = \frac{(P_C)^c (P_D)^d}{(P_A)^a (P_B)^b}$$

ii. Gather Data:
Take equilibrium concentrations or partial pressures for reactants and products.

iii. Determine Kc or Kp:
Plug in equilibrium concentrations into the equation:

$$K_c=\frac{[C{]}_{eq}^c[D{]}_{eq}^d}{[A{]}_{eq}^a[B{]}_{eq}^b}\text{or}{K}_p=\frac{(P_C{)}_{eq}^c(P_D{)}_{eq}^d}{(P_A{)}_{eq}^a(P_B{)}_{eq}^b}$$

4. Apply ICE Table if Necessary:
For initial concentrations and changes, apply an ICE table to find equilibrium concentrations.

This enables you to calculate the equilibrium constant from experimental results.