Question

Which solution, if either, would create the higher osmotic pressure (compared to pure water): one prepared from 1.0 g of NaCl in 10 mL of water or 1.0 g of CsBr in 10 mL of water

Answer 1

Answer: NaCl would give the higher pressure

Step-by-step explanation:

Osmotic pressure depends only on the number of ions.

NaCl dissociates as Na+ and Cl- ; CsBr dissociates as Cs+ and Br-

But the concentration of the solutions are different.

Concentration (morality ) of NaCl = Moles /Litre = (1 g /58.44g/mol)/0.01L

Total number of ions in NaCl solution = 2 x (1 g /58.44g/mol)/0.01L ( 1 mol NaCl gives 2 moles ions, 1 mol Na+ and 1 mol Cl-)

= 1.71×2RT

Similarly total number of ions in CsBr solution = 2 x (1 g /212.80 g/mol)/0.01L

= 0.47×2RT

Therefore osmotic pressure is higher in NaCl solution.