What is the osmotic pressure and molar concentration?

A)Isotonic saline solution, which has the same osomotic pressure as blood, can be prepared by dissolving 0.923g of NaCl in enough water to produce 100mL of solution. What is the osmotic pressure of this solution at 25C ?

B)Osmosis is the process responsible for carrying nutrients and water from groundwater supplies to the upper parts of trees. The osmotic pressures required for this process can be as high as 18.1atm . What would the molar concentration of the tree sap have to be to achieve this pressure on a day when the temperature is 25C?

Answer:
Use this equation, osmotic pressure = CRT,
where C is the concentration in molarity, R is the gas constant, and T is the temperature in Kelvin. So, the answers to your problems are:

A) osmotic pressure = CRT
to get C, get the number of moles of NaCl then divide it with volume of the solution
mole NaCl = 0.923g / 58.442 g/mol
mole NaCl = 0.0158 mol
C = 0.0158 mol / 0.1L
C = 0.158 mol/L
So,
osmotic pressure = 0.158 mol/L*(0.082058 L-atm/mol-K)*(25+273K)
osmotic pressure = 3.86 atm

B) C = osmotic pressure / RT
C = 18.1 atm / (0.082058 L-atm/mol-K * 298K)
C = 0.740 mol/L

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What is the osmotic pressure and molar concentration?

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