Molarity Problem... help please.. i have the answers

[coolchix321]

If 3x10^-7 moles NaCl is put into 100 mL and Ksp = 4 x 10^-10...
What molarity do you use for the Osmotic pressure?

Is it 2x10^-5 M (from Ksp) or 3x10^-6 M?

Thank you

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[coolchix321]

If 4 x 10^-5 moles NaCl are put into 200 mL and the Ksp is 4 x 10^-12 what is the Molarity and Osmotic pressure?

Is the Molarity for the Osmotic pressure: 2 x 10^-6 M (from Ksp)?

help is greatly appreciated
Thanks!

 

[Baylor2012]

Well...from my knowledge, I'm a bit rusty on this, I strongly belive that you'd solve it this way.

This is for the first question you posted***

For reference, osmotic pressure eqn. is = iMRT

Ksp=[(Na)(Cl)]/1 Thus, in effect Ksp= (x)^2

x= squareroot(4X10^-10)
X= 2 X 10^-5

X is your molarity, thus Molarity = 2X10^-5

On second thought I also see that you're trying to get the M just by taking moles/litres. But, I'd go with the method above because assuming that you are putting NaCl in 100ml of water, it would completely dissociate. And they also gave you Ksp, that implies it is more complex then what is give up frontSince it dissociates you'd have to use the Ksp. Looks a bit confusing, but if I were in your position, I would most likely stick with the method I gave you above.