Question

1) We have assumed that the unknown does not dissociate into more than one particle when

dissolved. If this was an incorrect assumption and the solid did dissociate slightly. Then how

would the calculated molar mass of solute from our experiment differ from the actual molar mass?

The calculated would be (too high, too low or unaffected) compared to the actual? Explain briefly.

2)If you measured the experimental freezing point of 30g cyclohexane with 0.012mols of Toluene

(MWT= 92.15) and compared it to a measurement of 30g cyclohexane with 0.012mols

benzophenone (MWT = 182.22). What would you expected to observe about the two separate

freezing points? Explain Briefly

3) Why is cyclohexane used as a solvent in this experiment instead of water? Water is much safer and much cheaper.

Answer 1

1) generally solute particles   can dissociate , associate and neither associate nor dissociate.

in case of dissociation observed molar mass will be less. compared to calculated   because in solution there will be more number of particles due to dissociation.

in case of association two or more molecules combine behave as one single molecule in that case observed molar mass will be large compared to calculated.

if solute neither associate or dissociate then observed molar mass will be close to calculated.

3) toulene and benzophenone can soluble only in organic solvents like cyclohexane   cannot soluble in water.

2) both the cases freezing point will decrease. and same value will decrease because both are same number of moles means same number of particles.   so colligative properties depends on number of particles not on mass.