Final answer:
The equilibrium potential for chloride (ECl) will change in response to the extracellular chloride concentration being 120 mM, as predicted by the Nernst equation.
Step-by-step explanation:
The question you've asked pertains to what happens to the equilibrium potential for chloride (ECl) when the extracellular chloride concentration is 120 mM. In biological systems, the equilibrium potential for an ion can be calculated using the Nernst equation. The Nernst equation states that the equilibrium potential for an ion is directly proportional to the logarithm of the ratio of external to internal ion concentration.
Since chloride is the predominant extracellular anion, any changes in the extracellular concentration will influence ECl. An increase in the extracellular chloride concentration from its standard physiological level (typically around 100 mM) to 120 mM would cause a shift in the electrical neutrality maintained by chloride ions in the extracellular fluid (ECF). The Nernst equation would predict a change in the chloride equilibrium potential in response to this altered ion concentration.