A metal chloride contains \( 55.0\% \) of chlorine by weight. \( 100 \, \text{mL} \) vapours of the metal chloride at STP weigh \( 0.57 \, \text{g} \). The molecular formula of the metal chloride is:
(Given: Atomic mass of chlorine is \( 35.5 \, \text{u} \))