On mixing 35 mL of acetone with 45 mL of chloroform, the total volume of the solution is

A mixture of chloroform $\left(CHC{l}_3\right)$ and acetone ${\left(C{H}_3\right)}_{2}CO$ slows negative deviations from Raoult’s law due to formation of hydrogen bonding between the two molecules.  Hence, a slight decrease in volume takes place.