What Is the Correct Molarity of Glucose for Isotonic IV Solutions?

[Torshi]

Human blood gives rise to an osmotic pressure of approximately 7.7 atm at body temperature, 35.9 Celsius.

What must the molarity of an intravenous glucose solution be to give rise to the same osmotic pressure as blood?

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I use the equation ; P=MRT if that's right
R is constant= .0821
T= 308.9 Kelvin
P=7.7 atm
M= ?

So would i rearrange the equation to P/RT=M
I get the wrong answer tho, and the answer doesn't sound right. I know I'm doing something wrong.

 

[pmsrw3]

What answer did you get, and how do you know it is wrong?

One thing: R is not 0.0821. It is 0.0821 L atm K^−1 mol^−1. Never let your numbers go out naked. Units are really, really important.

 

[pmsrw3]

bump

What answer did you get, and how do you know it's wrong?

 

[Torshi]

What answer did you get, and how do you know it's wrong?

.303 M

and masteringchemistry says it's wrong...

 

[pmsrw3]

Well, what you're doing looks right to me, and that answer is at least close to the correct concentration for isotonic glucose. All I can guess is that you need to have more or fewer sig figs, or maybe different units (e.g. 303 mM), or something like that.