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. Step 1: Understand the given information. The concentration of Mg²⁺ is provided as 3 mEq/L (milliequivalents per liter), and the volume of blood is 250 mL. The goal is to determine the mass of Mg²⁺ in milligrams.
2. Step 2: Convert the volume of blood from milliliters to liters, since the concentration is given in mEq/L. Use the conversion factor: 1 L = 1000 mL. The formula is: \( \text{Volume in liters} = \frac{\text{Volume in mL}}{1000} \).
3. Step 3: Calculate the total milliequivalents of Mg²⁺ in the given volume of blood. Use the formula: \( \text{Total mEq} = \text{Concentration (mEq/L)} \times \text{Volume (L)} \).
4. Step 4: Convert milliequivalents (mEq) to millimoles (mmol). For Mg²⁺, 1 mEq corresponds to 0.5 mmol because the charge of Mg²⁺ is +2. Use the formula: \( \text{mmol} = \text{mEq} \times 0.5 \).
5. Step 5: Convert millimoles to milligrams. The molar mass of Mg²⁺ is approximately 24.31 g/mol. Use the formula: \( \text{Mass in mg} = \text{mmol} \times \text{Molar mass (mg/mmol)} \), where \( \text{Molar mass (mg/mmol)} = 24.31 \).

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 valence of +2. Understanding mEq is crucial for converting between different units of concentration.

Concentration Calculation

Concentration calculation involves determining 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 in one liter of blood. To find the total amount in 250 mL, one must convert the volume from liters to milliliters and apply the concentration to find the total mEq present.

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. The conversion formula is: mg = mEq × (molecular weight / valence). This step is essential for translating the concentration of Mg²⁺ in mEq to its mass in mg, which is necessary for the final answer.