How many millimoles/L of chloride ions are contained in 1 litre of Potassium Chloride and Sodium Chloride infusion BP (the infusion fluid contains: potassium chloride 0.3%; sodium chloride 0.9%, molecular weight of potassium is 39, chloride is 35.5, and sodium is 23)? (3 marks)

Watch the units.

1 Mole of KCl will contain 1 Mol of Cl- ions

Same applies to NaCl

Number of Moles KCl in 1L:

0.3% KCl -> 0.3 g per 100 ml -> 3g per 1000ml

MW of KCl = 39 + 35.5 = 74.5g per Mole

Therefore 3/74.5 = 0.04 Mole per 1L

-> 40 mMol of KCl in 1 L

40 mMol of Cl- from KCl

Number of Moles NaCl in 1L:

0.9% NaCl -> 0.9g per 100ml -> 9 g per 1000 ml

MW of NaCl = 23 + 35.5 = 58.5

9/58.5 = 0.15384 Mol per L or 153.8 mMol/L = 153.8 mMol/L of Cl- from NaCl

Number of mMol of Cl- altogether in each litre of infusion:

153.8 + 40 = 193.8 mMol/L Cl-

Ref SPC