Products Up. Reactants Down. Coefficients Raised.

You'll learnhow to build an equilibrium expression from a balanced equation, one rule at a time.

Two students measure the same three concentrations and write down constants nine hundred apart, and nothing in the data decides between them — the expression does. Watch the quotient assemble piece by piece, then watch the upside-down version, which is not a small error but the constant for a different reaction. Twelve short steps; press Next for each one.

12 STEPS · 6 QUICK CHECKS · 2 SO₂ + O₂ ⇌ 2 SO₃ · K = [SO₃]² / ([SO₂]²[O₂]) = 30 · v4

the same expression, and only one way up

Before you start

What you're looking at

One settled flask of the SO2 / O2 / SO3 contact-process reaction, with the equilibrium expression assembling underneath it.

The question

Two flawless calculations give 30 and 0.033 from the same three numbers, so which one is actually K?

Step 1 / 12