At an osmotic pressure of 24 atm, what is the approximate concentration of NaCl in sea water?

• A. A. 0.25 M.
• B. B. 0.50 M.
• C. C. 0.75 M.
• D. D. 1.0 M.

Answer: (B)

To determine the concentration of NaCl in sea water at an osmotic pressure of 24 atm, we can use the concept of osmotic pressure, which is given by the formula:

[ \Pi = i \cdot C \cdot R \cdot T ]

where:

• ( \Pi ) is the osmotic pressure,

• ( i ) is the van 't Hoff factor (which is the number of particles the solute dissociates into),

• ( C ) is the molar concentration of the solute,

• ( R ) is the ideal gas constant, and

• ( T ) is the absolute temperature in Kelvin.

For NaCl, it dissociates into two ions: Na(^+) and Cl(^-). Therefore, the van 't Hoff factor ( i ) for NaCl is approximately 2.

Assuming a standard temperature (about 298 K), we can calculate the concentration ( C ) needed to reach an osmotic pressure of 24 atm. Rearranging the formula gives:

[ C = \frac{\Pi}{i \cdot R \cdot T} ]

Substituting the values into the equation:

• (