# A) In some regions of the southwest United States, the water is very hard

A) In some regions of the southwest United States, the water is very hard. For example, in Las Cruces, New Mexico, the tap water contains about 560 ug of dissolved solids per milliliter. Reverse osmosis units are marketed in this area of soften water. A typical unit exerts a pressure of 8.00 atm and can produce 45.0 liters of water per day. Assuming that all the dissolved solids are MgCO3 and assuming a temperature of 27&#8304;C, what total volume of water must be processed to produce 45.0 liters of pure water? (Hints: As pure water is produced, the remaining solution becomes more concentrated in the solute and its osmotic pressure increases. Reverse osmosis stops when the solution’s osmotic pressure reaches the applied pressure. The total number of moles of solute initially present in the total volume must remain in the residual solution.)

B) Would the same system described in part A work for purifying seawater? (Assume the seawater is 0.60 M NaCl.) Why or why not?
Please show all work and equations. College level question