Question

A solution is made by mixing 20.0 mL of toluene C6H5CH3d=0867gmL with 140.0 mL of benzene C6H6d=0874gmL. Assuming that the volumes add upon mixing, the molarity (M) and molality (m) of the toluene are?

Answer 1

There was a problem posted last night that used 150 mL benzene. Check to make sure that is not a typo.
Determine mass 20.0 mL toluene. Use density to do that. Then determine mols of toluene in that 20 mL.
Determine mass of benzene using density.
molality toluene = mols toluene/kg benzene.

Molarity toluene = mols/L .