Final answer:
The best descriptor for the solute concentration in a fluid considering electrolyte charge equivalency is 'mEq/L', which accounts for both ion numbers and their charges.
Step-by-step explanation:
Which of the following best describes the concentration of solute in a particular volume of fluid based on electrolyte charge equivalency? The correct option that describes this concentration is (C) mEq/L, which stands for milliequivalents per liter. The concept of milliequivalents (mEq) is crucial for electrolyte solutions where ions carry various charges. This measure of concentration considers both the number of ions and the charge on those ions. For instance, a 1 mol/L solution of Na+ (aq), which has a 1+ charge, is equivalent to 1 mEq/L. Conversely, a 1 mol/L solution of Ca2+ (aq) with a 2+ charge is equivalent to 2 mEq/L because each calcium ion carries two charges.