Kailey asked in Science & MathematicsBiology · 10 months ago

Bio 164 Help Please!!?

Why is an isotonic solution of glucose 0.3 but an isotonic solution of NaCl 0.15?

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  • 10 months ago

    NaCl is Na+ and Cl- giving 0.15 for each ion = total of 0.3.

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  • Ted K
    Lv 7
    10 months ago

    Osmolality of a molecule in solution is a function of the number of separate particles. One molecule of glucose is a single particle, but one molecule of sodium chloride splits into two separate particles (ions), one of Na+ and one of Cl-. And 0.15 x 2 = 0.3. So, in your example, although the molar concentration of glucose is twice that of NaCl, the osmolality is the same.  If you had 0.3 M NaCl, it's osmolality would be 0.3 x 2 = 0.6 oM.

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