ICE Table Calculator

It tracks initial concentration, change and equilibrium concentration for every species, expressing all of them in one unknown so the equilibrium expression becomes a single equation to solve.

Compare the reaction quotient Q, calculated from the starting concentrations, with K. Q below K means the reaction runs forward; Q above K means it runs in reverse; Q equal to K means it is already at equilibrium.

Only when K is small — conventionally when x works out under 5% of the smallest initial concentration. For a large K the reaction goes nearly to completion, x is not small at all, and the shortcut fails badly. This page never uses it.

Because the general equilibrium expression is a polynomial of degree a+b+c+d. Only the simplest stoichiometries reduce to a quadratic, so a numerical solver handles every case rather than only the textbook ones.

Yes, when the mixture starts with more product than equilibrium allows. A negative x simply means the reaction runs in the reverse direction, consuming product to make reactant.

By convention no, because each concentration is divided by a standard state of 1 M before the expression is evaluated. That is why K values are quoted as bare numbers.

No. Their concentration does not change as the reaction proceeds, so their activity is defined as 1 and they are omitted. That is why a heterogeneous equilibrium can have an expression with fewer terms than the equation has species.

Kc uses concentrations and Kp uses partial pressures. They are related by Kp = Kc(RT)^Δn, where Δn is the change in moles of gas. When Δn is zero the two are numerically equal.

Yes, and it is the only thing that does. Concentration, pressure and catalysts shift the position of equilibrium without changing K. The van 't Hoff equation describes how K varies with temperature, and the direction depends on whether the reaction is exothermic or endothermic.

Nothing to the position — it lowers the activation energy of the forward and reverse reactions equally, so equilibrium is reached faster at the same place. A catalyst changes rate, never yield at equilibrium.

Almost always because the textbook applied the small-x approximation and this page did not. When ionisation or extent of reaction is under about 5%, the two agree to the precision quoted; above it, the approximation drifts high and this page's exact figure is the correct one.

K above roughly 10³ means the reaction goes essentially to completion and the equilibrium mixture is nearly all product. K below roughly 10⁻³ means it barely proceeds. Between those, both reactants and products are present in meaningful amounts and the ICE table earns its keep.