Unit 41: Osmosis & Osmotic Pressure
Practice Problems
Note: problem difficulty is ranked using a star system.
(*) One-star problems are fundamental to the unit, and can be done relatively quickly. Use these problems to introduce yourself to the material.
(**) Two-star problems are more difficult, and require an understanding of one or two key concepts. Use these problems to test your understanding of the material.
(***) Three-star problems are the most difficult, and require some creative thinking in addition to a deep familiarity with multiple key concepts. Use these problems to challenge yourself; if you can complete one of these, you’re on your way to mastering the material.
*Q41.1) What’s the osmolarity of a 0.5 M solution of NaCl?
*Q41.2) What’s the osmotic pressure of a 0.5 M solution of NaCl at 27°C?
**Q41.3) 5g of NaCl (molar mass 58.44 g/mol) is dissolved in 2L of water at 4°C (where the density of water is 1.0 kg/L). The solution is then heated up to 95°C where the density of water is 0.95 kg/L. Calculate the osmolarity and osmolality of the solution at both temperatures.
***Q41.4) A cell is isotonic in 0.3 osmolar solution. What would happen to the cell when placed in each of the following solutions? If the cell’s volume should increase or decrease, by what percentage will it do so?
a) 0.15 M NaCl
b) 0.10 M NaCl
c) 0.15 M CaCl₂
d) 0.15 M NaCl + 0.15 M glycerol
e) Pure water