Which of the following ion is most abundant within cell fluid? — s Block Elements Chemistry Question

💡 Solution & Explanation

# Most Abundant Ion in Cell Fluid **Step 1: Identify what "cell fluid" means** Cell fluid refers to the intracellular fluid (ICF) inside cells, as opposed to extracellular fluid (ECF) outside cells. **Step 2: Recall the major ions in ICF vs ECF** - **Intracellular fluid (ICF):** Dominated by $K^+$ and $PO_4^{3-}$ (phosphate) - **Extracellular fluid (ECF):** Dominated by $Na^+$ and $Cl^-$ **Step 3: Determine the most abundant intracellular cation** The most abundant cation within cells is **$K^+$ (potassium ion)**, with concentration ~140 mEq/L inside cells compared to only ~5 mEq/L outside. **Step 4: Compare with anions** While phosphate ions are important intracellular anions, $K^+$ is more abundant overall in terms of molar concentration in the cytoplasm. --- **Answer B is correct** because **$K^+$ (potassium ion)** is the most abundant ion in intracellular fluid, maintained by the $Na^+/K^+$-ATPase pump. *(Note: Without seeing the options, if option B is $K^+$ or potassium ion, this explanation applies directly.)*