Concentrations come from the real rate laws with forward rate = k[reactants] and reverse rate = (k/K)[products], so the mixture always settles where Q = K. Particles are a small sample scaled to the amounts. K values are typical textbook or model values; temperature changes K through the van 't Hoff equation. Reactions are sped up so you can watch them.
Press Next step to build the table and the algebra one move at a time, or Show worked solution to watch it all. The small-x shortcut is tried first and checked with the 5% rule; if it fails, the quadratic formula takes over.
Press Show worked solution (or get it right) to watch the setup build step by step. In Kp problems the units of R and T cancel in red.
"Higher" or "lower" compares the NEW equilibrium with the equilibrium before the change. The watch animation runs the same rate laws as the reactor.
Your job
Drag a card onto a box, or tap a card and then tap the box's name. Cards are buttons, so Tab and Enter work too.
Wrong picks are fine here. Each one tells you why.