Learn how to calculate the milliequivalents (mEq/ml) of 50% magnesium sulfate solution. Understand the formula and steps to solve this common NAPLEX test prep question.
Table of Contents
Question
What is the mEq/ml (Milliequivalents) of 50% Magnesium Sulfate? (Molecular weight of MgSO is 120.4g/mol.)
A. 8.3mEq/ml
B. 4.11mEq/ml
C. 62mEq/ml
D. 50mEq/ml
E. 2.06mEq/ml
Answer
B. 4.11mEq/ml
Explanation
50gm/100ml × 1equiv/120.4gm × 1000meq/1equiv = 4.16meq/ml
To calculate the milliequivalents (mEq) of magnesium sulfate in a 50% solution, follow these steps:
1. Determine the molecular weight of MgSO4, which is 120.4 g/mol.
2. Calculate the weight of MgSO4 in 1 ml of a 50% solution:
50% = 500 mg/ml = 0.5 g/ml
3. Calculate the moles of MgSO4 in 1 ml of solution:
Moles = Weight / Molecular Weight
Moles = 0.5 g / 120.4 g/mol = 0.00415 mol/ml
4. Calculate the milliequivalents (mEq) of MgSO4:
MgSO4 has 2 equivalents per mole (Mg2+ and SO42-)
mEq = Moles × Equivalents
mEq = 0.00415 mol/ml × 2 eq/mol = 0.00830 eq/ml
5. Convert eq/ml to mEq/ml:
0.00830 eq/ml × 1000 = 8.30 mEq/ml
Therefore, a 50% magnesium sulfate solution contains 8.30 mEq/ml, which rounds to 8.3 mEq/ml, making B the correct answer.
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