Question

Which of the following solutions would have the lowest vapor pressure?

a. 1m glucose (C6H12O6)
b. 1m MgCl2
c. 1m NaNO3
d. 1m NaBr

Answer 1

the vapour pressure of a non-volatile, non-electrolyte solution is always lower than that of the vapour pressure of pure solvent.

Answer 2

what do you mean? i'm not seeing the connection.

btw: those little m's mean molality (moles solute/kg solvent)

Answer 3

hmm from the given choices, the molality does not matter because all of them are 1M. From the statement above, a non-electrolyte solution will always have a lower vapour pressure, so from the choices only glucose is non-electrolyte since it cannot dissociate to ions.

Answer 4

but lowest vapor pressure means highest intermolecular forces....? doesnt glucose only have london dispersion?

Answer 5

oops. sry ignore the above. i misunderstood my statement. The answer should be 1 mol MgCl2, since the molality is 1M so 3 mol/kg water (2 mol Cl- and 1 mol Mg2+). More particles, lower vapour pressure

Answer 6

so becaise it has 3 ions?

Answer 7

is that what seperates it from the other answers?

Answer 8

uhm its the no. of moles of solute
a. 1 mole solute
b. 3 mole solute
c. 2 mole solute (Na+ , NO3-)
d. 2 mole solute (Na+ , Br-)

Answer 9

more no. moles solute, lower the vapour pressure

Answer 10

gotcha. that makes sense. thank you so much.

Answer 11

np(: