Confusing MEQ question

[pharmacist007]

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Lactated Ringer’s Injection contains 20 mg of calcium chloride dihydrate per 100 ml of IV fluid. How many milliMoles of calcium are present in one liter of Lactated Ringer’s Injection? Molecular weights:
Ca = 40, Cl = 35.5, H = 1, O = 16

MW of calcium chloride dihdyrate would be 147

mmol = (drugs in grams / MW) *1000

20mg/100ml = 0.2g/l

(0.2g/147) *1000 = 1.36mmol/L

My question is why did they use MW as 147 when they ask for mmol of calcium and not calcium chloride dihydrate? Arent we suppose to use just MW of 40?

 

[Naplexfail]

Hi

We are going to use 147 and not 40 because we will equate the number of millimoles of calcium in calcium chlorate dihydrate.

One mmol of CaCl2 2H2O has one millimol of Calcium in it.

If this question were about sodium phosphate Na3PO4, then 1 mmol of Na3PO4 will have 3 mmols of sodium and we will use MW of Na3PO4 and not the MW of Na.

Hope this helps.

 

[pharmacist007]

Are these questions essentially the same? Both questions the answer being 333meq

A pharmacist has a bottle of Calcium Chloride that contain 24.5g. How many MEQ of Calcium Chloride are present? (MW of calcium chloride= 147)

A pharmacist has a bottle of Calcium Chloride that contain 24.5g. How many MEQ of Calcium are present? (MW of calcium chloride= 147)