# ICE table

An ICE table tracks Initial, Change and Equilibrium amounts to find an unknown equilibrium concentration. Let x be the change, use the coefficients for each species, then plug the equilibrium row into the K expression and solve for x.

Chemistry (university) · Part 07: Chemical equilibrium and solubility · Card 5 of 9 · Last updated 2026-10-19

## Analogy

Like a ledger: start balance, transactions, final balance.

## Example

**H₂ + I₂ ⇌ 2HI, K = 64**

Start: [H₂] = [I₂] = 1.0, [HI] = 0
Change: −x, −x, +2x
(2x)² / (1.0 − x)² = 64
x = 0.80, [HI] = 1.6 M

## In practice

Chemists use ICE tables to find how much of a weak acid or a gas mixture ends up as products.

## Practice

### Flashcards

- **What does ICE stand for?** Initial, Change, Equilibrium.

### Interview questions

**For H₂ + I₂ ⇌ 2HI with K = 64, find equilibrium concentrations starting from 1.0 M H₂ and 1.0 M I₂.**

- Set up an ICE table
- (2x)²/(1−x)² = 64
- Take square root: 2x/(1−x) = 8
- x = 0.80, so [HI] = 1.6 M and [H₂] = 0.20 M

## Questions people ask

### When can I ignore x in an ICE table?

If K is very small (below about 10⁻³) compared with the starting concentration, then x is tiny and 1.0 − x is almost 1.0. You can drop x from the subtraction. Check the answer: if x is under 5 percent of the starting amount, the shortcut is valid.

### What if the ICE equation needs a quadratic?

If the shortcut isn't allowed, expand the equation into ax² + bx + c = 0 and solve with the quadratic formula. Choose the root that gives non-negative concentrations for every species. The other root is not chemically possible and should be discarded.

## Related concepts

- [Equilibrium constant](https://studyvisually.com/learn/science/chemistry-university/chemistry-university-part-7/chemistry-university-part-7-concept-2)
- [Dynamic equilibrium](https://studyvisually.com/learn/science/chemistry-university/chemistry-university-part-7/chemistry-university-part-7-concept-1)
- [Reaction quotient](https://studyvisually.com/learn/science/chemistry-university/chemistry-university-part-7/chemistry-university-part-7-concept-3)
- [Kp and Kc](https://studyvisually.com/learn/science/chemistry-university/chemistry-university-part-7/chemistry-university-part-7-concept-4)

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