Question

multiple choice question
one millimole of nacl is dissolved in a liter of water. what is the concentration of na⁺ in the solution?
o 0.5 meq/l
o 1 meq/ml
o 1 meq/l
o 1 eq/l

Explanation:

Step1: Recall dissociation of NaCl

NaCl dissociates into Na⁺ and Cl⁻ in water. One mole of NaCl gives one mole of Na⁺. So, one millimole of NaCl gives one millimole of Na⁺.

Step2: Recall the definition of milliequivalent

For a monovalent ion like Na⁺, 1 millimole = 1 milliequivalent.

Step3: Calculate the concentration

The volume of the solution is 1 liter and the amount of Na⁺ is 1 milliequivalent. Concentration = $\frac{\text{amount of solute}}{\text{volume of solution}}$. So the concentration of Na⁺ is $\frac{1\ mEq}{1\ L}=1\ mEq/L$.

Answer:

1 mEq/L (corresponding to the option "1 mEq/L")