Chem Problem
posted by Student .
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!

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