Help Gen Chem Question (osmotic pressure)

[752779]

This is an AAMC practice test (actual previous MCAT exam)

Which ideal solution exhibits the greatest osmotic pressure?

A. 0.1 M MgCl2
B. 0.2 M NaCl
C. 0.2 M CaCl2
D. 0.5 M Glucose

I thought glucose molecular weight is 180 g/mol, it's a big molecule contains 6 carbons, 12 hydrogens, and 6 oxygens. Therefore it has more attract force.

The answer to this question is C. AAMC explains, " the solution listed has the greatest concentration of solute particles. CaCl2 dissociates into 3 ions, making solution listed 0.6 M in solute particles."

If glucose were to dissociates wouldn't has the greatest concentration of solute particles?

Please explain in details..

Thanks

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[Astra]

http://study.com/cimages/multimages/16/osmosis4d.png


The van hoff't factor is determined by the number of ions in solution.


So, we can see that A and C will have the highest number of ions.

Now look at their concentrations. CaCl2 has a higher concentration and this makes it have the highest osmotic pressure

 

[theonlytycrane]

@trandzuyhieu glucose doesn't dissociate spontaneously. it has a van't hoff factor of 1.

 

[aldol16]

If glucose were to dissociates wouldn't has the greatest concentration of solute particles?

Exactly what do you think it dissociates into?

 

[752779]

Thank you all.. the last time I took chemistry was in 2004, that was some times ago....

 

[Doc2martin]

Thank you all.. the last time I took chemistry was in 2004, that was some times ago....

i never learned it in gen chem, or in biology. the only time i was required to learn this was for the MCAT

 

[Dorctor princess]

osmotic pressure = van's hoff factor X R X Molar concentration X temp. C is the best answer because if we multiply the concentration with the van's hoff factor== C is the highest-- assuming R and Temp are constant for all