Question

Consider two solutions, one formed by adding 10 g of glucose (c6h12o6) to 1 l of water and the other formed by adding 10 g of sucrose (c12h22o11) to 1 l of water. are the vapor pressures over the two solutions the same?

Answer 1

Relative lowering of vapour pressure is a colligative property

The colligative property depends upon the number of solute particles.

More the number of solute (non volatile) particles more the relative lowering of vapour pressure of solution.

The molar mass of sucrose is higher than the molar mass of glucose

thus for each gram of glucose and sucrose the moles of glucose will be more than the moles of sucrose.

hence for 10g of both glucose and sucrose

the moles of glucose will be more than moles of sucrose

Due to more number of molecules of non volatile solute in the solution of 10g of glucose the lowering of vapour pressure will be more in glucose solution.

hence the vapour pressure over glucose solution will be less than the vapour pressure over sucrose solution.

Answer: No,the vapor pressures over the two solutions will not be the same