(type 3) Calculate mg per volume from mEq per volume
5. mEq and mOsmol 5.1) mEq 5.1.1) mEq - General
5.1.1.1) mEq from weight/volume Normal 1
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If lithium carbonate solution is mentioned as 121.62 mEq/L, then express the strength in percent w/v. Round your answer to the nearest hundredth. The molecular weight of lithium carbonate is 74 g/mol.
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lb equals 0.45 % kg
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The molecular weight of lithium carbonate = 74.
Valence or charge = 2.
Therefore, we can write: 74 mg = 2 mEq.
Percent (w/v) is the number of grams of solute present per 100 mL of the solution.
Since the question needs g/100 mL as the final unit, we keep 74 mg in the starting numerator. So, 2 mEq will be the denominator.
Also, the solution contains 121.62 mEq per L; therefore, the mEq is used as the denominator for the second fraction, in order to cancel out. The dimensional analysis will be like this:
`(121.62 \quad mEq)/(1 \quad L) × (74 \quad mg)/(2 \quad mEq) × (1 \quad L)/(1000 \quad mL) `
` × (1 \quad g)/(1000 \quad mg) × (100 \quad mL)/(100 \quad mL) = (0.45 \quad g)/(100 \quad mL)`.
Therefore, it's 0.45% (w/v). Ans.