Question

A solution contains the following ions: K+(13.2 mEq/L​),Mg₂+(15.8mEq​/L), and Sr₂+(3.5mEq/L​), if HCO₃​ is the only anion present in the solution, what is its concentration in mEq/L​ ? Round your answer to 3 significant figures.

Answer 1

The concentration of the anion HCO₃⁻ in the solution is 51.8 mEq/L. This is calculated by summing the total positive charge from the cations (K⁺, Mg²⁺, and Sr²⁺) and ensuring charge balance, since HCO₃⁻ is the only anion present.

Step-by-step explanation:

To calculate the concentration of the anion HCO₃⁻ in the solution, we need to ensure charge balance in the solution. This means the total positive charge, contributed by the cations, must equal the total negative charge, contributed by the anions.

For monovalent cations (like K⁺), the milliequivalents per liter (mEq/L) are equal to the molar concentration. However, for divalent cations (like Mg²⁺ and Sr²⁺), the mEq/L is twice the molar concentration, because each ion contributes two positive charges.

Now, we sum up the charges from each cation:

K⁺: 13.2 mEq/LMg²⁺: 15.8 mEq/L × 2 = 31.6 mEq/L Sr²⁺: 3.5 mEq/L × 2 = 7 mEq/L

Adding these together, we get the total positive charge in the solution:

13.2 mEq/L + 31.6 mEq/L + 7 mEq/L = 51.8 mEq/L

Since HCO₃⁻ is the only anion present and it is monovalent, its concentration will also be 51.8 mEq/L to balance the total positive charge of the cations.