Chemistry · Chapter 13

Build K, Then Read Its Size

Pick a reaction and the expression for K is drawn for you, with pure solids and liquids struck out. Then see how far that reaction really goes from a 0.100 M start.

The expression products on top, each raised to its coefficient

The equilibrium constant expression for the chosen reaction

Every tile above the bar is a product. Every tile below it is a reactant. The small number at a tile's corner is the coefficient from the balanced equation.

How far it goes solved from 0.100 M of each reactant

Equilibrium concentrations from a 0.100 molar start

These bars are not a guess. The model solves the K expression for the extent of reaction x, then fills in every concentration and checks the answer against K.

Where this K sits the scale runs by powers of ten

The size of K on a powers of ten scale

Choose a reaction

The two constants

0.0046Kc reactants favored
Measured at 298 K
Gas moles: right 2, left 1, so Δn = +1
R T = 24.47 L·atm/mol
(R T)Δn = 24.47
Kp = 0.113

Feel the (R T)Δn factor

298 K

This slider changes only the conversion factor, so you can see how Δn and T work together. The measured K values belong to the temperature listed above.

At this T, (R T)Δn = 24.47
which would give Kp = 0.113
Reading the result
A small K
Pick a reaction to see what its constant promises.