Acetone is mixed with bleaching powder to give

Acetone forms chloroform when it undergoes haloform reaction with bleaching powder (CaOCl₂).

$\begin{array}{l}\underset{\mathrm{Bleaching} \mathrm{powder}}{{\mathrm{CaOCl}}_2}+{\mathrm{H}}_2\mathrm{O}\to \mathrm{Ca}(\mathrm{OH}{)}_2+{\mathrm{Cl}}_2\\ \underset{\mathrm{Acetone}}{{\mathrm{CH}}_3{\mathrm{COCH}}_3}+3{\mathrm{Cl}}_2\to {\mathrm{CCl}}_3{\mathrm{COCH}}_3+3\mathrm{HCl}\\ 2{\mathrm{CCl}}_3{\mathrm{COCH}}_3+\mathrm{Ca}(\mathrm{OH}{)}_2\to \underset{\text{ chloroform }}{2{\mathrm{CHCl}}_3}+{\left({\mathrm{CH}}_3\mathrm{COO}\right)}_2\mathrm{Ca}\end{array}$