Compartment 1 Compartment 2 Begin 0.15M 0.15M K in Compartment 2 Nat in Compartment I KCI (b) BUT only K can move K Na Ion movement: Kt crosses into K Compartment 1 Nat Nat stays in Compartment 1 K At the potassium K equilibrium potential buildup of positive charge in Compartment I produces an electrical potential that exactly offsets the K chemical concentration gradientBegin: K+ in Compartment 2, Na+ in Compartment 1; BUT only K+ can move. Ion movement: K+ crosses into Compartment 1; Na+ stays in Compartment 1. buildup of positive charge in Compartment 1 produces an electrical potential that exactly offsets the K+ chemical concentration gradient. At the potassium equilibrium potential: