Type 2: Find the weight of the solute from mOsmol and volume

5. mEq and mOsmol 5.2) mOsmol 5.2.1) mOsmol - General

5.2.1.1) mOsmol - General Normal 1


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If calcium chloride solution is expressed as 0.5405 mOsmol/mL, then how many milligrams of calcium chloride will be present in each 50 mL of the solution? The molecular weight of calcium chloride is 111 g/mol.


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lb equals 1000 mg/50mL kg

    For calcium chloride , the 'golden formula' is:
    1 mmol = `[111]` mg = `[2]` mEq = `[3]` mOsmol.

    Since we need mg in the numerator of the desired unit, we begin with keeping it in the numerator of the first fraction.
    Again, since 0.5405 mOsmol is contained in 1 mL of solution, we keep the 0.5405 mOsmol in the numerator of the second fraction for getting the 'mOsmol' part cancelled out.
    Using dimensional analysis:
    `(111 \quad mg)/(3 \quad mOsmol) × (0.5405 \quad mOsmol)/(1 \quad mL) × (50 \quad mL)/(50 \quad mL)= 1000 \quad (mg)/(50 \quad mL)` Ans.