The typical concentration of Mg²⁺ in blood is 3 mEq/L. How many milligrams of Mg²⁺ are in 250 mL of blood?

Verified step by step guidance

1. Understand that mEq/L stands for milliequivalents per liter, which is a unit of concentration.
2. Recognize that the charge of Mg²⁺ is +2, meaning 1 equivalent of Mg²⁺ is equal to 1 mole of Mg²⁺ ions divided by 2.
3. Convert the concentration from mEq/L to mmol/L by using the fact that 1 mEq of Mg²⁺ is equivalent to 0.5 mmol of Mg²⁺.
4. Calculate the number of millimoles of Mg²⁺ in 250 mL of blood by using the concentration in mmol/L and the volume in liters.
5. Convert the millimoles of Mg²⁺ to milligrams by using the molar mass of magnesium (24.305 g/mol).

Key Concepts

Milliequivalents (mEq)

Milliequivalents (mEq) is a unit of measurement used to express the concentration of ions in a solution. It accounts for the charge of the ion, allowing for a standardized way to compare different ions. For magnesium (Mg²⁺), 1 mEq corresponds to 1 millimole of the ion, considering its divalent charge.

Concentration Calculation

Concentration refers to the amount of a substance in a given volume of solution. In this case, the concentration of Mg²⁺ is given as 3 mEq/L, which means there are 3 milliequivalents of magnesium per liter of blood. To find the total amount in a different volume, such as 250 mL, one must convert the volume to liters and apply the concentration.

Conversion from mEq to mg

To convert milliequivalents (mEq) of an ion to milligrams (mg), one must use the molecular weight of the ion. For magnesium, the atomic weight is approximately 24.3 g/mol. Since 1 mEq of Mg²⁺ equals 12.15 mg (24.3 g/mol divided by 2), this conversion is essential for determining the mass of magnesium in the specified volume of blood.