[SP0RT0]

Hoping this is the correct forum (I'm not a chem student, I'm an engineer).  I'm trying to calculate the osmolarity of the components of sports drinks.  I've been able to calculate NaCl, KCl, CHO and the other easy components, but I'm struggling with citric acid (anhydrous), CaCO3, and trimagnesium dicitrate.  I have the mw (192, 100 and 451 respectively), for input to the osmolarity calc, but when it comes to the number of particles, I'm unsure how these three components dissociate in water.  Please help.

[Borek]

These are not trivial. Citric acid is a weak acid and you actually need to calculate degree of dissociation for at least first two dissociation steps. CaCO₃ will most likely neutralize some of the citric acid producing Ca²⁺ and CO₂ (which will leave the solution). Trimagnesium dicitrate is the worst one, easier to measure than to calculate - but perhaps its amount is low enough to be negligible compared to NaCl/KCl?

[SP0RT0]

Thanks - yes, good point re the very small amounts of mg, and ca for that matter, contributing only a few mmol/L.  I'll dig deeper into the citric acid dissociation.