Concentration change and equilibrium

The video tutorial explains the concept of the reaction quotient QC and its relationship with the equilibrium constant KC. It discusses how the addition of hydrogen gas and hydrogen iodide to a reaction mixture affects chemical equilibrium. The video details how these additions create stress, disturb equilibrium, and how the system responds to restore balance through forward and backward reactions. The tutorial concludes with a summary of how changes in reactant or product concentrations impact the reaction quotient and equilibrium.

How does the reaction quotient QC relate to the equilibrium constant KC when the concentration of reactants or products changes?

What is the significance of the reaction quotient QC in understanding chemical equilibrium?