ICE Table Calculator

Results

The reaction changed a starting concentration by 78 %, more than 5 %, so a shortcut that drops x from a (C − x) term would have been wrong. The answer here solves the full equation.

Rounded to 3 significant figures, the fewest in the values you entered.

Concentrations are in mol/L. For gases you can enter partial pressures in atm instead, and K is then Kp.

How to Use the ICE Table Calculator

1. 1. Enter the reaction. Use ⇌, <=> or =, for example H2(g) + I2(g) <=> 2HI(g). Coefficients you type are used as written; with none typed, the equation is balanced for you. Mark a pure solid or liquid with (s) or (l) and it is left out of K.
2. 2. Choose what to find. Pick equilibrium concentrations from K to solve for x, K from equilibrium concentrations if you have measured them all, or K from the start and one equilibrium value for the classic ICE problem.
3. 3. Enter the numbers. Concentrations are in mol/L, and a blank starting concentration means zero. For gases you can use partial pressures in atm and read K as Kp.
4. 4. Read the table. The Initial, Change and Equilibrium columns appear with x, the direction the mixture shifts, and the working.

How an ICE Table Works

An ICE table tracks one reaction from its starting mixture to equilibrium. The I row holds the starting concentrations. The C row says how each concentration changes: the reaction advances by an amount x, so a reactant falls by its coefficient times x and a product rises by its coefficient times x. The E row adds the two. Substituting the E row into the equilibrium expression gives one equation in x.

aA + bB ⇌ cC + dD

−ax, −bx, +cx, +dx

[A]₀ − ax, [B]₀ − bx, [C]₀ + cx, [D]₀ + dx

K = [C]^c [D]^d ÷ ([A]^a [B]^b)

Pure solids and liquids are left out of K because their concentration does not change. Because K depends on the equation as written, reversing it gives 1/K and doubling every coefficient squares K; that is why this calculator uses your coefficients rather than silently reducing them.

Worked Example: H₂ + I₂ ⇌ 2HI

The calculator opens with K = 50.0 and 1.00 M each of H₂ and I₂, with no HI. The ICE table has H₂ and I₂ at 1.00 − x and HI at 2x, so the equation to solve is (2x)² ÷ ((1.00 − x)(1.00 − x)) = 50.0. Taking the square root of both sides gives 2x ÷ (1.00 − x) = 7.07, so x = 0.780.

• [H₂] = [I₂] = 1.00 − 0.780 = 0.220 M
• [HI] = 2 × 0.780 = 1.56 M
• Q₀ = 0 is less than K = 50.0, so the reaction ran forward, as expected with no product present

Check by substituting back: 1.56² ÷ 0.220² = 50.3. It is not exactly 50.0 only because the concentrations are rounded to three figures; the calculator solves with full precision and rounds at the end.

The 5 % Rule and Why This Tool Skips It

Textbook problems often drop x from a term like (C − x) when K is small, which turns a quadratic into a square root. The usual test is that x comes out below 5 % of the starting concentration. This calculator does not need the shortcut, because it solves the full equation numerically, but it reports how large x was so you can see whether the shortcut would have passed. For 0.100 M acetic acid, CH₃CO₂H ⇌ H⁺ + CH₃CO₂⁻ with K = 1.8 × 10⁻⁵, x is 1.3 × 10⁻³ M, which is 1.3 % of the starting concentration. The shortcut works there; for a stronger acid at low concentration it can fail.

Common Mistakes

• Forgetting the coefficient on x. For 2HI the change is 2x, and in the expression it is squared.
• Including solids and liquids in K. Their concentrations are constant, so they are left out.
• Using K for a different form of the equation. K for the reverse reaction is 1/K; for a halved equation it is √K.
• Mixing up Kc and Kp. Use concentrations for Kc and partial pressures for Kp; do not combine them in one table.

Frequently Asked Questions

What does ICE stand for in chemistry?

It stands for Initial, Change, Equilibrium: the three rows of the table. It is a bookkeeping method for equilibrium problems that keeps track of how each concentration moves from the start to equilibrium.

How do you set up an ICE table?

Write the balanced equation across the top, put the starting concentrations in the I row, then in the C row put −coefficient × x for each reactant and +coefficient × x for each product. Add the rows to get E, then substitute the E row into K and solve for x.

How do you find K from an ICE table?

Substitute the equilibrium row into K = products^coefficients ÷ reactants^coefficients. If you know the start and one equilibrium value, use that value to find x first, which fills in the rest of the table, then compute K.

When can you ignore x in an ICE table?

When K is small enough that x is under 5 % of the starting concentration, you can treat (C − x) as C. Check afterwards: if x turns out larger than 5 %, the shortcut was not valid and you need the quadratic or a numerical solution, which is what this calculator uses.

What if the value of x is negative?

A negative x means the reaction runs in reverse: reactants form and products are used up. This happens when the starting mixture has more product than equilibrium allows, that is, when Q is greater than K. Concentrations must still end up positive.

Does K have units?

In thermodynamics K is dimensionless, because it is defined with activities. Many courses write units such as M^-1 for Kc, which depend on the reaction. This calculator treats K as a plain number and does not attach units.