Posted by **Student** on Friday, March 1, 2013 at 9:26pm.

I need help solving this question, I have no idea what I'm supposed to do.

What is the minimum pressure in kPa that must be applied at 25 °C to obtain pure water by reverse osmosis from water that is 0.165 M in sodium chloride and 0.029 M in magnesium sulfate? Assume complete dissociation for electrolytes.

I know that the equation for osmosis is

pi= MRT, but how am I supposed to find pressure from that. do I use the r value of 0.018 because it's units include that of atm? Or do I solve for r?

Please help!

- Chem Problem -
**bobpursley**, Friday, March 1, 2013 at 9:36pm
VonHOffpressure=iMRT

i is von hoff constant (number ions per particle)

M is molarity

R is universal gas constant

T is temperature in Kelvins

for NaCl, i=2; for MgSO4, i=2

figure the pressure for each, then add

R is 0.08205746(14) Lâ€‰atmâ€‰Kâˆ’1â€‰molâˆ’1

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